Dates and Time Planning
The calendar quirks that make simple-sounding date math surprisingly hard — month overflow, ISO weeks, business days, fiscal quarters, and where the 7-day week even came from.
Try the 2 Weeks From Today Calculator →Why Adding “One Month” to a Date Is Harder Than It Sounds
“Add one month” sounds like the simplest possible date operation. It isn’t — and the reason is one specific date that breaks more naive…
Dates and TimeISO Week Numbers Explained — Why Week 1 Doesn’t Always Start on January 1
If you’ve ever seen a date labeled “Week 52” or “Week 1” on a business report and wondered why it didn’t line up with your mental math of…
Dates and TimeHow Business-Day Calculations Handle Federal Holidays
“Ten business days” sounds like a precise, unambiguous instruction, but getting the actual resulting date right requires accounting for…
Dates and TimeWhy Pregnancy Is Dated From the Last Period, Not From Conception
Pregnancy dating trips up a lot of people the first time they see it, because the standard counting method doesn’t start where most people…
Dates and TimeWhat Fiscal Quarters Are and Why Companies Plan Around Them
“Q1,” “Q3,” and similar shorthand show up constantly in business news and reporting, and most people assume every company’s quarters line…
Dates and TimeA Short History of the 7-Day Week — Why We Use It At All
Days are set by Earth’s rotation. Years are set by Earth’s orbit. Months loosely track the moon’s cycle. The 7-day week is the odd one out…