ConvertTime
Blog
Read articles about time zones, daylight saving time, productivity tips for global teams, and time-management best practices. New posts added regularly.
ISO week numbers — what they are and how to calculate them
ISO weeks are 1-53. Week 1 contains January 4 (or the first Thursday). Here's how the system works.
Latest articles
The math of leap years — why every 4 years isn't always right
Leap years are every 4 years, except every 100, except every 400. Here's the math and why 1900 wasn't a leap year but 2000 was.
How many weekdays until [event]?
Counting weekdays until your event excludes weekends and (optionally) holidays. Here's how to calculate it correctly.
Pregnancy due date math — counting from LMP vs conception
Pregnancy due date is calculated from LMP, not conception — usually 280 days. Here's the math and how ultrasound dating refines it.
The Julian day number — counting days from 4713 BC
The Julian day number counts days from 4713 BC. It's used in astronomy and ancient history. Here's how it works and why.
Convert epoch timestamp to human time — and back
Convert Unix epoch timestamps to human-readable dates and back. Quick reference and the math behind it.
How to add or subtract days from a date (without spreadsheet errors)
Adding 30 days to a date is simple in concept. In practice — Excel sometimes gets it wrong. Here's how to do it right.
Calculating duration between two dates and times
Calculating time between two dates seems simple but has edge cases. Here's how to handle DST, leap years, and time zones.
How many business days are in a year? (And why it matters)
A typical year has 252 business days in the US — but the number varies by country. Here's the breakdown and why it matters.
Best apps and tools for travelers crossing time zones
Apps and tools for managing time zones while traveling — world clocks, jet lag calculators, flight trackers, and more.