RockQuickDates

This module allows you to quickly connect a datefrom and a dateto field and calculate a duration, plus it adds buttons to quickly set the date/time of both fields in customisable increments:

Setup

// eg in /site/ready.php
rockquickdates()->addToField('from', [
  'roundto' => '-15m',
]);
rockquickdates()->addToField('to', [
  'roundto' => '+15m',
]);
rockquickdates()->addDuration(
  'hours', // the duration field
  'from', // the start field
  'to', // the end field
  'h' // the duration type (hours, minutes, seconds)
);