Even with libraries, DST creates headaches. Just having an hour of ambiguous time (Nov 4, 1:23am 2018 has two possible meanings in most places) means having to

Even with libraries, DST creates headaches. Just having an hour of ambiguous time (Nov 4, 1:23am 2018 has two possible meanings in most places) means having to write test cases, parse log files differently and there are areas (e.g. database) where you can't use a library and if you're not able to structure your application to store UTC timestamps, you have to account for it yourself. Libraries are great at abstracting away a lot of the pain, but some of the complexity will always leak through that abstraction.