📅 Date & Time

Date and time tools handle the calendar maths that trips people up: days between dates, age in years months and days, day of the week for any date, adding and subtracting durations, time zone conversions, and working days between dates. The calculations follow the Gregorian calendar and account for leap years. Each page explains the counting rule it uses, because conventions differ, for example whether the start date is included in a count. Worked examples show the method applied to real dates. All of it runs in your browser, nothing is stored, and the results include enough intermediate detail that you can verify the count by hand. The date pages also cover recurring patterns such as weekly schedules and anniversary counts, with the calendar conventions stated on each page.