Resource Types
DateTime
Date/Time
PHP Manual

# Predefined Constants

The DATE_ constants are defined since PHP 5.1.1 and they offer standard date representations, which can be used along with the date format functions (like date).

Following constants exists since PHP 5.1.2 and specify a format returned by functions date_sunrise and date_sunset.

`SUNFUNCS_RET_TIMESTAMP` (integer)
  Timestamp
`SUNFUNCS_RET_STRING` (integer)
  Hours:minutes (example: 08:02)
`SUNFUNCS_RET_DOUBLE` (integer)
  Hours as floating point number (example 8.75)