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Jun 24, 2013. There are a lot of functions in PHP for dealing with date, time or timestamp. For a Beginner it might be trouble to choose the rights ones, although it's really easy. In this post, I will especially Deal with the situation, where you fetched a Date from MySQL/PostgreSQL table, and you need to display it in a. Name & Description. 1, ADDDATE(). 2, ADDTIME(). 3, CONVERT_TZ(). Converts from one timezone to another. 4, CURDATE(). Returns the current date. 5, CURRENT_DATE(), CURRENT_DATE. Synonyms for CURDATE(). 6, CURRENT_TIME(), CURRENT_TIME. Synonyms for CURTIME().

1. Date Functions In Access
2. Mysql Get Date

This section describes the functions that can be used to manipulate temporal values. See Section 11.3, “Date and Time Types”, for a description of the range of values each date and time type has and the valid formats in which values may be specified.

Table 12.13 Date and Time Functions

Here is an example that uses date functions. The following query selects all rows with a date_col value from within the last 30 days:

The query also selects rows with dates that lie in the future.

Functions that expect date values usually accept datetime values and ignore the time part. Functions that expect time values usually accept datetime values and ignore the date part.

Functions that return the current date or time each are evaluated only once per query at the start of query execution. This means that multiple references to a function such as NOW() within a single query always produce the same result. (For our purposes, a single query also includes a call to a stored program (stored routine, trigger, or event) and all subprograms called by that program.) This principle also applies to CURDATE(), CURTIME(), UTC_DATE(), UTC_TIME(), UTC_TIMESTAMP(), and to any of their synonyms.

The CURRENT_TIMESTAMP(), CURRENT_TIME(), CURRENT_DATE(), and FROM_UNIXTIME() functions return values in the current session time zone, which is available as the session value of the time_zone system variable. In addition, UNIX_TIMESTAMP() assumes that its argument is a datetime value in the session time zone. See Section 5.1.13, “MySQL Server Time Zone Support”.

Some date functions can be used with “zero” dates or incomplete dates such as '2001-11-00', whereas others cannot. Functions that extract parts of dates typically work with incomplete dates and thus can return 0 when you might otherwise expect a nonzero value. For example:

Other functions expect complete dates and return NULL for incomplete dates. These include functions that perform date arithmetic or that map parts of dates to names. For example:

Several functions are more strict when passed a DATE() function value as their argument and reject incomplete dates with a day part of zero. These functions are affected: CONVERT_TZ(), DATE_ADD(), DATE_SUB(), DAYOFYEAR(), LAST_DAY() (permits a day part of zero), TIMESTAMPDIFF(), TO_DAYS(), TO_SECONDS(), WEEK(), WEEKDAY(), WEEKOFYEAR(), YEARWEEK().

Date Functions In Access

Fractional seconds for TIME, DATETIME, and TIMESTAMP values are supported, with up to microsecond precision. Functions that take temporal arguments accept values with fractional seconds. Return values from temporal functions include fractional seconds as appropriate.

Mysql Get Date

• ADDDATE(date,INTERVAL exprunit), ADDDATE(expr,days)

  When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVALunit argument, see Temporal Intervals.

  When invoked with the days form of the second argument, MySQL treats it as an integer number of days to be added to expr.

• ADDTIME() adds expr2 to expr1 and returns the result. expr1 is a time or datetime expression, and expr2 is a time expression.

• CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value. Time zones are specified as described in Section 5.1.13, “MySQL Server Time Zone Support”. This function returns NULL if the arguments are invalid.

  If the value falls out of the supported range of the TIMESTAMP type when converted from from_tz to UTC, no conversion occurs. The TIMESTAMP range is described in Section 11.1.2, “Date and Time Type Overview”.

  To use named time zones such as 'MET' or 'Europe/Amsterdam', the time zone tables must be properly set up. For instructions, see Section 5.1.13, “MySQL Server Time Zone Support”.

• Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

• CURRENT_DATE, CURRENT_DATE()

  CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE().

• CURRENT_TIME, CURRENT_TIME([fsp])

  CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().

• CURRENT_TIMESTAMP, CURRENT_TIMESTAMP([fsp])

  CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW().

• Returns the current time as a value in 'hh:mm:ss' or hhmmss format, depending on whether the function is used in a string or numeric context. The value is expressed in the session time zone.

  If the fsp argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

• Extracts the date part of the date or datetime expression expr.

• DATEDIFF() returns expr1 − expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

• DATE_ADD(date,INTERVAL exprunit), DATE_SUB(date,INTERVAL exprunit)

  These functions perform date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is evaluated as a string; it may start with a - for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted.

  For more information about temporal interval syntax, including a full list of unit specifiers, the expected form of the expr argument for each unit value, and rules for operand interpretation in temporal arithmetic, see Temporal Intervals.

  The return value depends on the arguments:

  • DATE if the date argument is a DATE value and your calculations involve only YEAR, MONTH, and DAY parts (that is, no time parts).

  • DATETIME if the first argument is a DATETIME (or TIMESTAMP) value, or if the first argument is a DATE and the unit value uses HOURS, MINUTES, or SECONDS.

  • String otherwise.

  To ensure that the result is DATETIME, you can use CAST() to convert the first argument to DATETIME.

• Formats the date value according to the format string.

  The specifiers shown in the following table may be used in the format string. The % character is required before format specifier characters. The specifiers apply to other functions as well: STR_TO_DATE(), TIME_FORMAT(), UNIX_TIMESTAMP().

  Specifier	Description
  %a	Abbreviated weekday name (Sun..Sat)
  %b	Abbreviated month name (Jan..Dec)
  %c	Month, numeric (0..12)
  %D	Day of the month with English suffix (0th, 1st, 2nd, 3rd, …)
  %d	Day of the month, numeric (00..31)
  %e	Day of the month, numeric (0..31)
  %f	Microseconds (000000..999999)
  %H	Hour (00..23)
  %h	Hour (01..12)
  %I	Hour (01..12)
  %i	Minutes, numeric (00..59)
  %j	Day of year (001..366)
  %k	Hour (0..23)
  %l	Hour (1..12)
  %M	Month name (January..December)
  %m	Month, numeric (00..12)
  %p	AM or PM
  %r	Time, 12-hour (hh:mm:ss followed by AM or PM)
  %S	Seconds (00..59)
  %s	Seconds (00..59)
  %T	Time, 24-hour (hh:mm:ss)
  %U	Week (00..53), where Sunday is the first day of the week; WEEK() mode 0
  %u	Week (00..53), where Monday is the first day of the week; WEEK() mode 1
  %V	Week (01..53), where Sunday is the first day of the week; WEEK() mode 2; used with %X
  %v	Week (01..53), where Monday is the first day of the week; WEEK() mode 3; used with %x
  %W	Weekday name (Sunday..Saturday)
  %w	Day of the week (0=Sunday..6=Saturday)
  %X	Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
  %x	Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v
  %Y	Year, numeric, four digits
  %y	Year, numeric (two digits)
  %%	A literal % character
  %x	x, for any “x” not listed above

  Ranges for the month and day specifiers begin with zero due to the fact that MySQL permits the storing of incomplete dates such as '2014-00-00'.

  The language used for day and month names and abbreviations is controlled by the value of the lc_time_names system variable (Section 10.15, “MySQL Server Locale Support”).

  For the %U, %u, %V, and %v specifiers, see the description of the WEEK() function for information about the mode values. The mode affects how week numbering occurs.

  DATE_FORMAT() returns a string with a character set and collation given by character_set_connection and collation_connection so that it can return month and weekday names containing non-ASCII characters.

• See the description for DATE_ADD().

• DAY() is a synonym for DAYOFMONTH().

• Returns the name of the weekday for date. The language used for the name is controlled by the value of the lc_time_names system variable (Section 10.15, “MySQL Server Locale Support”).

• Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero day part.

• Returns the weekday index for date (1 = Sunday, 2 = Monday, …, 7 = Saturday). These index values correspond to the ODBC standard.

• Returns the day of the year for date, in the range 1 to 366.

• The EXTRACT() function uses the same kinds of unit specifiers as DATE_ADD() or DATE_SUB(), but extracts parts from the date rather than performing date arithmetic. For information on the unit argument, see Temporal Intervals.

• Given a day number N, returns a DATE value.

  Use FROM_DAYS() with caution on old dates. It is not intended for use with values that precede the advent of the Gregorian calendar (1582). See Section 12.8, “What Calendar Is Used By MySQL?”.

• Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD hh:mm:ss' or YYYYMMDDhhmmss.uuuuuu format, depending on whether the function is used in a string or numeric context. unix_timestamp is an internal timestamp value representing seconds since '1970-01-01 00:00:00' UTC, such as produced by the UNIX_TIMESTAMP() function.

  The return value is expressed in the session time zone. (Clients can set the session time zone as described in Section 5.1.13, “MySQL Server Time Zone Support”.) The format string, if given, is used to format the result the same way as described in the entry for the DATE_FORMAT() function.

  If you use UNIX_TIMESTAMP() and FROM_UNIXTIME() to convert between values in a non-UTC time zone and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For details, see the description of the UNIX_TIMESTAMP() function.

• Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions.

  The possible values for the first and second arguments result in several possible format strings (for the specifiers used, see the table in the DATE_FORMAT() function description). ISO format refers to ISO 9075, not ISO 8601.

  Function Call	Result
  GET_FORMAT(DATE,'USA')	'%m.%d.%Y'
  GET_FORMAT(DATE,'JIS')	'%Y-%m-%d'
  GET_FORMAT(DATE,'ISO')	'%Y-%m-%d'
  GET_FORMAT(DATE,'EUR')	'%d.%m.%Y'
  GET_FORMAT(DATE,'INTERNAL')	'%Y%m%d'
  GET_FORMAT(DATETIME,'USA')	'%Y-%m-%d %H.%i.%s'
  GET_FORMAT(DATETIME,'JIS')	'%Y-%m-%d %H:%i:%s'
  GET_FORMAT(DATETIME,'ISO')	'%Y-%m-%d %H:%i:%s'
  GET_FORMAT(DATETIME,'EUR')	'%Y-%m-%d %H.%i.%s'
  GET_FORMAT(DATETIME,'INTERNAL')	'%Y%m%d%H%i%s'
  GET_FORMAT(TIME,'USA')	'%h:%i:%s %p'
  GET_FORMAT(TIME,'JIS')	'%H:%i:%s'
  GET_FORMAT(TIME,'ISO')	'%H:%i:%s'
  GET_FORMAT(TIME,'EUR')	'%H.%i.%s'
  GET_FORMAT(TIME,'INTERNAL')	'%H%i%s'

  TIMESTAMP can also be used as the first argument to GET_FORMAT(), in which case the function returns the same values as for DATETIME.

• Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23.

• Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid.

• LOCALTIME, LOCALTIME([fsp])

  LOCALTIME and LOCALTIME() are synonyms for NOW().

• LOCALTIMESTAMP, LOCALTIMESTAMP([fsp])

  LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW().

• Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result is NULL.

• Returns a time value calculated from the hour, minute, and second arguments.

  The second argument can have a fractional part.

• Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999.

• Returns the minute for time, in the range 0 to 59.

• Returns the month for date, in the range 1 to 12 for January to December, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero month part.

• Returns the full name of the month for date. The language used for the name is controlled by the value of the lc_time_names system variable (Section 10.15, “MySQL Server Locale Support”).

• Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss' or YYYYMMDDhhmmss format, depending on whether the function is used in a string or numeric context. The value is expressed in the session time zone.

  If the fsp argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

  NOW() returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, NOW() returns the time at which the function or triggering statement began to execute.) This differs from the behavior for SYSDATE(), which returns the exact time at which it executes.

  In addition, the SET TIMESTAMP statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE(). Setting the timestamp to a nonzero value causes each subsequent invocation of NOW() to return that value. Setting the timestamp to zero cancels this effect so that NOW() once again returns the current date and time.

  See the description for SYSDATE() for additional information about the differences between the two functions.

• Adds N months to period P (in the format YYMM or YYYYMM). Returns a value in the format YYYYMM.

  The period argument P is not a date value.

• Returns the number of months between periods P1 and P2. P1 and P2 should be in the format YYMM or YYYYMM. Note that the period arguments P1 and P2 are not date values.

• Returns the quarter of the year for date, in the range 1 to 4.

• Returns the second for time, in the range 0 to 59.

• Returns the seconds argument, converted to hours, minutes, and seconds, as a TIME value. The range of the result is constrained to that of the TIME data type. A warning occurs if the argument corresponds to a value outside that range.

• This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts. If the date, time, or datetime value extracted from str is illegal, STR_TO_DATE() returns NULL and produces a warning.

  The server scans str attempting to match format to it. The format string can contain literal characters and format specifiers beginning with %. Literal characters in format must match literally in str. Format specifiers in format must match a date or time part in str. For the specifiers that can be used in format, see the DATE_FORMAT() function description.

  Scanning starts at the beginning of str and fails if format is found not to match. Extra characters at the end of str are ignored.

  Unspecified date or time parts have a value of 0, so incompletely specified values in str produce a result with some or all parts set to 0:

  Range checking on the parts of date values is as described in Section 11.3.1, “The DATE, DATETIME, and TIMESTAMP Types”. This means, for example, that “zero” dates or dates with part values of 0 are permitted unless the SQL mode is set to disallow such values.

  If the NO_ZERO_DATE or NO_ZERO_IN_DATE SQL mode is enabled, zero dates or part of dates are disallowed. In that case, STR_TO_DATE() returns NULL and generates a warning:

  You cannot use format '%X%V' to convert a year-week string to a date because the combination of a year and week does not uniquely identify a year and month if the week crosses a month boundary. To convert a year-week to a date, you should also specify the weekday:

• SUBDATE(date,INTERVAL exprunit), SUBDATE(expr,days)

  When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVALunit argument, see the discussion for DATE_ADD().

  The second form enables the use of an integer value for days. In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression expr.

• SUBTIME() returns expr1 − expr2 expressed as a value in the same format as expr1. expr1 is a time or datetime expression, and expr2 is a time expression.

• Returns the current date and time as a value in 'YYYY-MM-DD hh:mm:ss' or YYYYMMDDhhmmss format, depending on whether the function is used in a string or numeric context.

  If the fsp argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

  SYSDATE() returns the time at which it executes. This differs from the behavior for NOW(), which returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, NOW() returns the time at which the function or triggering statement began to execute.)

  In addition, the SET TIMESTAMP statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE().

  Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is nondeterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging.

  Alternatively, you can use the --sysdate-is-now option to cause SYSDATE() to be an alias for NOW(). This works if the option is used on both the master and the slave.

  The nondeterministic nature of SYSDATE() also means that indexes cannot be used for evaluating expressions that refer to it.

• Extracts the time part of the time or datetime expression expr and returns it as a string.

  This function is unsafe for statement-based replication. A warning is logged if you use this function when binlog_format is set to STATEMENT.

• TIMEDIFF() returns expr1 − expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type.

  The result returned by TIMEDIFF() is limited to the range allowed for TIME values. Alternatively, you can use either of the functions TIMESTAMPDIFF() and UNIX_TIMESTAMP(), both of which return integers.

• TIMESTAMP(expr), TIMESTAMP(expr1,expr2)

  With a single argument, this function returns the date or datetime expression expr as a datetime value. With two arguments, it adds the time expression expr2 to the date or datetime expression expr1 and returns the result as a datetime value.

• Adds the integer expression interval to the date or datetime expression datetime_expr. The unit for interval is given by the unit argument, which should be one of the following values: MICROSECOND (microseconds), SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

  The unit value may be specified using one of keywords as shown, or with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are legal.

• Returns datetime_expr2 − datetime_expr1, where datetime_expr1 and datetime_expr2 are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part '00:00:00' where necessary. The unit for the result (an integer) is given by the unit argument. The legal values for unit are the same as those listed in the description of the TIMESTAMPADD() function.

  The order of the date or datetime arguments for this function is the opposite of that used with the TIMESTAMP() function when invoked with 2 arguments.

• This is used like the DATE_FORMAT() function, but the format string may contain format specifiers only for hours, minutes, seconds, and microseconds. Other specifiers produce a NULL value or 0.

  If the time value contains an hour part that is greater than 23, the %H and %k hour format specifiers produce a value larger than the usual range of 0..23. The other hour format specifiers produce the hour value modulo 12.

• Returns the time argument, converted to seconds.

• Given a date date, returns a day number (the number of days since year 0).

  TO_DAYS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable. See Section 12.8, “What Calendar Is Used By MySQL?”, for details.

  Remember that MySQL converts two-digit year values in dates to four-digit form using the rules in Section 11.3, “Date and Time Types”. For example, '2008-10-07' and '08-10-07' are seen as identical dates:

  In MySQL, the zero date is defined as '0000-00-00', even though this date is itself considered invalid. This means that, for '0000-00-00' and '0000-01-01', TO_DAYS() returns the values shown here:

  This is true whether or not the ALLOW_INVALID_DATES SQL server mode is enabled.

• Given a date or datetime expr, returns the number of seconds since the year 0. If expr is not a valid date or datetime value, returns NULL.

  Like TO_DAYS(), TO_SECONDS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable. See Section 12.8, “What Calendar Is Used By MySQL?”, for details.

  Like TO_DAYS(), TO_SECONDS(), converts two-digit year values in dates to four-digit form using the rules in Section 11.3, “Date and Time Types”.

  In MySQL, the zero date is defined as '0000-00-00', even though this date is itself considered invalid. This means that, for '0000-00-00' and '0000-01-01', TO_SECONDS() returns the values shown here:

  This is true whether or not the ALLOW_INVALID_DATES SQL server mode is enabled.

• If UNIX_TIMESTAMP() is called with no date argument, it returns a Unix timestamp representing seconds since '1970-01-01 00:00:00' UTC.

  If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' UTC. The server interprets date as a value in the session time zone and converts it to an internal Unix timestamp value in UTC. (Clients can set the session time zone as described in Section 5.1.13, “MySQL Server Time Zone Support”.) The date argument may be a DATE, DATETIME, or TIMESTAMP string, or a number in YYMMDD, YYMMDDhhmmss, YYYYMMDD, or YYYYMMDDhhmmss format. If the argument includes a time part, it may optionally include a fractional seconds part.

  The return value is an integer if no argument is given or the argument does not include a fractional seconds part, or DECIMAL if an argument is given that includes a fractional seconds part.

  When the date argument is a TIMESTAMP column, UNIX_TIMESTAMP() returns the internal timestamp value directly, with no implicit “string-to-Unix-timestamp” conversion.

  The valid range of argument values is the same as for the TIMESTAMP data type: '1970-01-01 00:00:01.000000' UTC to '2038-01-19 03:14:07.999999' UTC. If you pass an out-of-range date to UNIX_TIMESTAMP(), it returns 0.

  If you use UNIX_TIMESTAMP() and FROM_UNIXTIME() to convert between values in a non-UTC time zone and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For example, due to conventions for local time zone changes such as Daylight Saving Time (DST), it is possible for UNIX_TIMESTAMP() to map two values that are distinct in a non-UTC time zone to the same Unix timestamp value. FROM_UNIXTIME() will map that value back to only one of the original values. Here is an example, using values that are distinct in the MET time zone:

  To use named time zones such as 'MET' or 'Europe/Amsterdam', the time zone tables must be properly set up. For instructions, see Section 5.1.13, “MySQL Server Time Zone Support”.

  If you want to subtract UNIX_TIMESTAMP() columns, you might want to cast them to signed integers. See Section 12.10, “Cast Functions and Operators”.

• UTC_DATE, UTC_DATE()

  Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

• UTC_TIME, UTC_TIME([fsp])

  Returns the current UTC time as a value in 'hh:mm:ss' or hhmmss format, depending on whether the function is used in a string or numeric context.

  If the fsp argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

• UTC_TIMESTAMP, UTC_TIMESTAMP([fsp])

  Returns the current UTC date and time as a value in 'YYYY-MM-DD hh:mm:ss' or YYYYMMDDhhmmss format, depending on whether the function is used in a string or numeric context.

  If the fsp argument is given to specify a fractional seconds precision from 0 to 6, the return value includes a fractional seconds part of that many digits.

• This function returns the week number for date. The two-argument form of WEEK() enables you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the value of the default_week_format system variable is used. See Section 5.1.8, “Server System Variables”.

  The following table describes how the mode argument works.

  Mode	First day of week	Range	Week 1 is the first week …
  0	Sunday	0-53	with a Sunday in this year
  1	Monday	0-53	with 4 or more days this year
  2	Sunday	1-53	with a Sunday in this year
  3	Monday	1-53	with 4 or more days this year
  4	Sunday	0-53	with 4 or more days this year
  5	Monday	0-53	with a Monday in this year
  6	Sunday	1-53	with 4 or more days this year
  7	Monday	1-53	with a Monday in this year

  For mode values with a meaning of “with 4 or more days this year,” weeks are numbered according to ISO 8601:1988:

  • If the week containing January 1 has 4 or more days in the new year, it is week 1.

  • Otherwise, it is the last week of the previous year, and the next week is week 1.

  If a date falls in the last week of the previous year, MySQL returns 0 if you do not use 2, 3, 6, or 7 as the optional mode argument:

  One might argue that WEEK() should return 52 because the given date actually occurs in the 52nd week of 1999. WEEK() returns 0 instead so that the return value is “the week number in the given year.” This makes use of the WEEK() function reliable when combined with other functions that extract a date part from a date.

  If you prefer a result evaluated with respect to the year that contains the first day of the week for the given date, use 0, 2, 5, or 7 as the optional mode argument.

  Alternatively, use the YEARWEEK() function:

• Returns the weekday index for date (0 = Monday, 1 = Tuesday, … 6 = Sunday).

• Returns the calendar week of the date as a number in the range from 1 to 53. WEEKOFYEAR() is a compatibility function that is equivalent to WEEK(date,3).

• Returns the year for date, in the range 1000 to 9999, or 0 for the “zero” date.

• YEARWEEK(date), YEARWEEK(date,mode)

  Returns year and week for a date. The year in the result may be different from the year in the date argument for the first and the last week of the year.

  The mode argument works exactly like the mode argument to WEEK(). For the single-argument syntax, a mode value of 0 is used. Unlike WEEK(), the value of default_week_format does not influence YEARWEEK().

  The week number is different from what the WEEK() function would return (0) for optional arguments 0 or 1, as WEEK() then returns the week in the context of the given year.