PHP references - PHP date, time and calendar conversions

List of PHP date and time functions
FUNCTION	DESCRIPTION
checkdate()	Checks date.
date()	Formats a local date and time.
date_add()	Adds date
date_create()	Creates new Date object.
date_create_from_format()	Creates a new Date object from format.
date_default_timezone_get()	Gets default timezone.
date_default_timezone_set()	Sets default timezone.
date_format()	Formats date.
date_time_set()	Sets time.
date_timestamp_get()	Gets timestamp.
date_timestamp_set()	Sets timestamp.
date_timezone_get()	Gets timezone.
date_timezone_set()	Sets timezone.
getdate()	Gets date and time information.
gettimeofday()	Gets current time.
gmdate()	Formats a GMT/UTC date and time.
gmmktime()	Gets Unix based GMT timestamp.
gmstrftime()	Formats a GMT/UTC date and time according local setting.
time()	Gets current Unix based timestamp.

List of PHP date and time predefined constants
CONSTANT	DESCRIPTION
SUNFUNC_RET_TIMESTAMP	Returns timestamp.
SUNFUNC_RET_STRING	Sets hours and minutes.
SUNFUNC_RET_DOUBLE	Sets floating hours and minutes.

List of PHP calendar functions
FUNCTION	DESCRIPTION
cal_days_in_month	Returns number of days in a month.
cal_from_jd	Converts from Julian calendar to local.
cal_info	Returns information about calendar.
cal_to_jd	Converts from local calendar to Julian.
easter_date	Provides Unix based timestamp for Easter midnight on current year.
easter_days	Provides number of days after March 21st on which Easter falls.
frenchtojd	Converts from French Republican calendar to Julian.
gregoriantojd	Converts from Gregorian calendar to Julian.
jddayofweek	Returns the day of the week.
jdmonthname	Returns the month name.
jdtofrench	Converts from Julian calendar to French Republican.
jdtogregorian	Converts from Julian calendar to Gregorian.
jdtojewish	Converts from Julian calendar to Jewish.
jdtojulian	Converts Julian day count to Julian calendar date.
jdtounix	Converts from Julian Unix timestamp.
jewishtojd	Converts Jewish calendar to Julian.
juliantojd	Converts Julian calendar date to Julian day count.
unixtojd	Converts from Unix timestamp to Julian.