I can see great answers, so there's no need to repeat here, so I'd like to offer some advice:
I would recommend using a Unix Timestamp integer instead of a human-readable date format to handle time internally, then use PHP's date()
function to convert the timestamp value into a human-readable date format for user display. Here's a crude example of how it should be done:
// Get unix timestamp in seconds
$current_time = date();
// Or if you need millisecond precision
// Get unix timestamp in milliseconds
$current_time = microtime(true);
Then use $current_time
as needed in your app (store, add or subtract, etc), then when you need to display the date value it to your users, you can use date()
to specify your desired date format:
// Display a human-readable date format
echo date('d-m-Y', $current_time);
This way you'll avoid much headache dealing with date formats, conversions and timezones, as your dates will be in a standardized format (Unix Timestamp) that is compact, timezone-independent (always in UTC) and widely supported in programming languages and databases.