Sooner or later, we all have to save a date somewhere, sending it to a database or saving it into a file. Maybe we will be converting it into JSON to send it to another software.
Many database systems do not track time zones. Some of them have a configuration option that states what time zone they should work with, but in most cases, the date you provide will be saved as is.
This leads to unexpected bugs or behaviors in many cases. Suppose you were a good boy scout and properly did all the work required to receive a datetime preserving its time zone. Now you have a datetime of 2018-01-15 15:30:00 UTC+01:00 and, once you store it in your database, UTC+01:00 will easily be lost, even if you store it in a file yourself, storing and restoring the time zone is usually a bothersome work.
For this reason, you should always ensure you convert your datetimes to UTC before...
