Guides
Understand the numbers
These articles explain the rules behind the calculators: how days are counted, how time zones actually shift, and where unit differences come from. Read one, then use the tool with more confidence.
6 articles
- 2026-10-196 min read
How to Count the Days Between Two Dates
The arithmetic is simple, but the ambiguity is not. How to count calendar days, when to include the end date, and where leap years actually change the answer.
Read the guide - 2026-10-195 min read
Business Days, Weekends and Public Holidays
Why five business days is not five days, how to count working days by hand, and why public holidays make cross-border deadlines harder than they look.
Read the guide - 2026-10-196 min read
Time Zone Conversion: Five Mistakes That Cost a Meeting
Offsets are not fixed, dates change more often than you expect, and daylight saving does not switch everywhere on the same day. How to convert times without getting it wrong.
Read the guide - 2026-10-197 min read
Metric and Imperial Conversions That People Get Wrong
Exact conversion factors for length, mass, area and volume, why area and volume surprise people, and the difference between US and Imperial measures.
Read the guide - 2026-10-195 min read
Celsius, Fahrenheit and Kelvin Without the Confusion
The three temperature scales, the exact formulas, why a simple multiplier never works, and the anchors that let you check any result in your head.
Read the guide - 2026-10-196 min read
Deadlines, Notice Periods and Date Arithmetic
How to count a notice period backwards, what “one month” means in a contract, how month-end and leap days break naive arithmetic, and how to record a deadline defensibly.
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