Date

Definition

Lightweight, high-performance date/time handling for the fpx preprocessor This module provides a compact datetime type and essential operations used primarily for expanding the standard predefined macros:

• __DATE__ → e.g. 'Aug-12-2025'
• __TIME__ → e.g. '14:35:27'
• __TIMESTAMP__ → e.g. 'Tue 12-Aug-2025 14:35:27'

Features:

• now() returns current local date/time using date_and_time()
• Flexible string formatting via to_string(fmt)
• Parsing from common string formats (ISO, US, RFC-like)
• Day-of-week calculation via Zeller’s congruence
• Elemental and pure functions where possible for performance
• Minimal memory footprint using small integer kinds (int8, int16)

Used internally by fpx_macro during __DATE__, __TIME__, and __TIMESTAMP__ expansion.

Examples

1. Expand standard predefined macros (as done internally):

   type(datetime) :: dt
   dt = now()
   print *, '__DATE__      >> ', dt%to_string('MMM-dd-yyyy')      ! __DATE__      >> 'Aug-12-2025'
   print *, '__TIME__      >> ', dt%to_string('HH:mm:ss')          ! '__TIME__      >> 14:35:27'
   print *, '__TIMESTAMP__ >> ', dt%to_string('ddd-MMM-yyyy HH:mm:ss') ! '__TIMESTAMP__ >> Tue 12-Aug-2025 14:35:27'
   ...

2. Parse date from string:

   type(datetime) :: build_time
   build_time = datetime('2025-08-12 09:30:00')
   print *, 'build on: ', build_time%to_string('ddd-MMM-yyyy')
   ...

3. Get current time for logging:

   type(datetime) :: dt
   dt = now()
   print *, 'Preprocessing started at ', dt%to_string('HH:mm:ss')
   ...

Data Types
type	datetime
	Compact representation of date and time Stores all components in minimal integer kinds to reduce memory usage. All fields are public for easy access. More...

Methods

datetime_parse()

elemental subroutine datetime_parse ( class(datetime), intent(inout) this, character(*), intent(in) string, character(*), intent(in), optional fmt )

private

Parse date/time from string using common formats.

Supports ISO, US, and abbreviated month formats. On error, defaults to Unix epoch (1970-01-01 00:00:00) Perform conversion to ISO string

• d: Represents the day of the month as a number from 1 through 31.
• dd: Represents the day of the month as a number from 01 through 31.
• ddd: Represents the abbreviated name of the day (Mon, Tues, Wed, etc).
• dddd: Represents the full name of the day (Monday, Tuesday, etc).
• h: 12-hour clock hour (e.g. 4).
• hh: 12-hour clock, with a leading 0 (e.g. 06)
• H: 24-hour clock hour (e.g. 15)
• HH: 24-hour clock hour, with a leading 0 (e.g. 22)
• m: Minutes
• mm: Minutes with a leading zero
• M: Month number(eg.3)
• MM: Month number with leading zero(eg.04)
• MMM: Abbreviated Month Name (e.g. Dec)
• MMMM: Full month name (e.g. December)
• s: Seconds
• ss: Seconds with leading zero
• t: Abbreviated AM / PM (e.g. A or P)
• tt: AM / PM (e.g. AM or PM
• y: Year, no leading zero (e.g. 2015 would be 15)
• yy: Year, leading zero (e.g. 2015 would be 015)
• yyy: Year, (e.g. 2015)
• yyyy: Year, (e.g. 2015)

Remarks

Definition at line 243 of file date.f90.

datetime_to_string()

character(:) function, allocatable datetime_to_string ( class(datetime), intent(in) this, character(*), intent(in), optional fmt )

private

Format datetime as string using flexible format codes Supports many common patterns including those required for __DATE__ and __TIMESTAMP__. Default format: 'yyyy-MM-ddTHH:mm:ss'.

Remarks

Definition at line 357 of file date.f90.

now()

type(datetime) function, public now

Return current local date and time Uses intrinsic date_and_time() and populates all fields including milliseconds.

Returns

the datetime object corresponding to the current time

Remarks

Definition at line 164 of file date.f90.

weekday()

pure elemental integer function weekday ( class(datetime), intent(in) this )

private

Returns the day of the week calculated using Zeller's congruence. Returned value is an integer scalar in the range [0-6], such that:

• 0: Sunday
• 1: Monday
• 2: Tuesday
• 3: Wednesday
• 4: Thursday
• 5: Friday
• 6: Saturday

Remarks

Definition at line 192 of file date.f90.