Posts on date math edge cases, business-day counting, and timezone gotchas.https://date.tooljo.com/en-ushttps://date.tooljo.com/blog/dst-and-date-math/https://date.tooljo.com/blog/dst-and-date-math/DST transitions take an hour out of November and add one in March. If you do day-count arithmetic in local time, you'll be off by ±1 day twice a year. Here's why and how to fix it.Tue, 28 Apr 2026 00:00:00 GMThttps://date.tooljo.com/blog/inclusive-vs-exclusive-day-counting/https://date.tooljo.com/blog/inclusive-vs-exclusive-day-counting/Vacation accruals, free-trial periods, prison sentences, lease terms. The same 'X days' means different counts depending on the contract — and the bug is usually in software that picks the wrong one.Tue, 28 Apr 2026 00:00:00 GMT