How to calculate and verify JAN and EAN barcode check digits
The modulus 10, weight 3-1 method, by hand and in a spreadsheet.
Guides: Converters
Guides in Converters, newest first.
How to convert binary, decimal, and hexadecimal numbers
Place values, working it out by hand, and negative or very large numbers.
Is a Unix timestamp UTC? Timestamps vs. time zones
Why one value shows different times and dates by zone and daylight saving.
How to distinguish Unix timestamp seconds from milliseconds
Use the digit count and the converted date to tell which unit you have.
What to check when converting between YAML and JSON
Comments, types, anchors, and keys that get lost or change meaning.