PHP Dates and Times Converting Time and Date Parts to an Epoch Timestamp

PHP Dates and Times

Converting Time and Date Parts to an Epoch Timestamp

Problem

You want to know what epoch timestamp corresponds to a set of time and date parts.

Solution

Example   Getting a specific epoch timestamp

            // 7:45:03 PM on March 10, 1975, local time
            // Assuming your "local time" is US Eastern time
            $then = mktime(19,45,3,3,10,1975);

Use gmmktime(), as in Example, if your time and date parts are in GMT.


Example   Getting a specific GMT-based epoch timestamp

            // 7:45:03 PM on March 10, 1975, in GMT
            $then = gmmktime(19,45,3,3,10,1975);

Use DateTime::createFromFormat(), as in Example, if your time and date parts are in a formatted time string.


Example   Getting a specific epoch timestamp from a formatted time string

            // 7:45:03 PM on March 10, 1975, in a particular timezone
            $then = DateTime::createFromFormat(DateTime::ATOM, "1975-03-10T19:45:03-04:00");


Discussion

The functions mktime() and gmmktime() each take a date and time’s parts (hour, minute, second, month, day, year) and return the appropriate Unix epoch timestamp. The components are treated as local time by mktime(), while gmmktime() treats them as a date and time in UTC.

In Example, $stamp_future is set to the epoch timestamp for 3:25 P.M. on December 3, 2024. The epoch timestamp can be fed back to date() to produce a formatted time string.


Example   Working with epoch timestamps

            date_default_timezone_set('America/New_York');
            // $stamp_future is 1733257500
            $stamp_future = mktime(15,25,0,12,3,2024);
            // $formatted is '2024-12-03T15:25:00-05:00'
            $formatted = date('c', $stamp_future);

Because the calls to mktime() in Example were made with the time zone set to America/New_York, using gmmktime() instead produces epoch timestamps that are 18,000 seconds (five hours) smaller, as shown in Example.


Example   Epoch timestamps and gmmktime()

            date_default_timezone_set('America/New_York');
            // $stamp_future is 1733239500, whch is 18000
            // smaller than 1733257500
            $stamp_future = gmmktime(15,25,0,12,3,2024);

The createFromFormat() method of the DateTime class behaves more flexibly. Instead of accepting already-chopped-up time parts, you give it a formatted time or date string and tell it the structure of that string. It then decomposes the parts properly and calculates the correct timestamp. 


Table   Format characters for DateTime::createFromFormat( )

Character          Meaning                                                                                                                       
space or tab

#                        Any one of the separation bytes ;, :, /, ., ,, -, (, )

;, :, /, ., ,, -, (, )   Literal character

?                        Any byte (not a character, just one byte)

*                        Any number of bytes until the next digit or separation character

!                         Resetall fieldsto“startof Unixepoch”values(without this,any unspecified fields will be
                          set to the currrent date/time) 

|                         Reset any unparsed fields to “start of Unix epoch” values

+                        Treat unparsed trailing data as a warning rather than an error
________________________________________________________________________________


Example  shows how DateTime::createFromFormat() can be used to get time parts out of a larger string.

Example   Using DateTime::createFromFormat( )

            $text = "Birthday: May 11, 1918.";
            $when = DateTime::createFromFormat("*: F j, Y.|", $text);
            // $formatted is "Saturday, 11-May-18 00:00:00 UTC"
            $formatted = $when->format(DateTime::RFC850);