It is a good video. The good thing about using a library like Kalends is that it takes into account everything he mentions about different timezones into account. Just tell it the time, date, and timezone name.

Just be careful about generalizing too much and assuming things such as: "this time will exist again tomorrow". Or "next month also has a 31st day". Or "DST is always a 3600 second difference from standard time".

Here is another article I wrote which also talks about some pitfalls of time and timezones: http://www.creativedeletion.com/2015/01/28/falsehoods-progra...