Time and Date
Age, durations and working-day calculators for everyday date math.
Date math looks simple until you actually try to do it by hand, working out someone's exact age in years, months and days needs careful borrowing across months of different lengths, counting business days between two dates means correctly excluding weekends without an off-by-one error, and none of it stays simple once leap years enter the picture. This category covers age and date-difference calculators, working-day and duration calculators, and time-zone conversion tools, all built on calendar-aware date arithmetic rather than naive day-counting, so leap years, varying month lengths and daylight-saving transitions are handled automatically instead of silently producing a wrong answer. These calculators are useful for anything from filling out a form that asks for exact age, to working out a project deadline that only counts business days, to coordinating a meeting across time zones without doing the offset math yourself. Each one shows its full working, not just a final number, so you can see exactly how the date difference was calculated.