UTC

Java

• https://stackoverflow.com/questions/6850874/how-to-create-a-java-date-object-of-midnight-today-and-midnight-tomorrow
• https://stackoverflow.com/questions/9629636/get-todays-date-in-java-at-midnight-time/31683549

C#

• https://alexandrebrisebois.wordpress.com/2013/04/07/midnight-universal-time-is-not-midnight-local-time/
• https://stackoverflow.com/questions/51221139/c-sharp-get-midnight-time-of-specific-timezone-in-utc

Perl

• http://blogs.perl.org/users/tom_wyant/2017/11/what-time-is-midnight.html

Ruby

• https://stackoverflow.com/questions/43124628/ruby-time-object-for-midnight-utc/43128254

PHP

• https://stackoverflow.com/questions/36371687/how-to-convert-date-to-utc-midnight-using-php

Python

• https://stackoverflow.com/a/55870204

Swift

• https://stackoverflow.com/questions/26189656/how-can-i-set-an-nsdate-object-to-midnight