See date
$dateIso8601 = date('c');
time()
Unix timestamp (in second) One hour ago
$time = time() - 3600;
$date = new DateTime();
$date->modify('+1 day');
$expirationTime = new DateTime();
$expirationTime->modify('+'.$cacheIntervalInSecond.' seconds')
$dateInputFormat = 'Y-m-d H:i:s';
$date = DateTime::createFromFormat($dateInputFormat, "2017-09-18 12:20:22");
$dateInputFormat = 'Y-m-d H:i:s';
$date = DateTime::createFromFormat($dateInputFormat, "2017-09-18 12:20:22");
$date->getTimestamp();
string date ( string $format [, int $timestamp = time() ] )
Example
date('l jS \of F Y h:i:s A',1391624456)
Wednesday 5th of February 2014 07:20:56 PM
$datetime->format('Y-m-d');
$diff = $sourceModifiedTime->diff($compiledModifiedTime);
$daysBetween = $diff->format('%a');
$secondsBetween = $diff->format('%s');
round((time() - $timestampCreation)/60/60/24)
For Datetime
$dateTime1 > $dateTime2