Time Tools

Measures the time between two dates in years, months, weeks and days, with the total in days and hours, and gives a clock time’s mirror across the 12–6 line and its opposite (the hour + 6, the minutes + 30). A month added to 31 January ends on the last day of February. ISO 8601 writes such a duration as P1Y2M10D, each part counted in the calendar.

• ISO 8601-1:2019, Date and time — Representations for information interchange — Part 1: Basic rules (durations)
• Edward M. Reingold and Nachum Dershowitz, Calendrical Calculations, 4th ed. (Cambridge University Press, 2018)