Hours & Time Duration Counter
Pick a start and end time — see total hours and decimal hours instantly. Handles overnight shifts.
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Overnight shifts wrap automatically (e.g. 22:00 → 06:00 = 8 hours).
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Hours & Duration — answers & formulas
Deep-dive formulas, definitions, and worked examples — indexed for search and ready to share.
Math HistoryItaly · c. 1425
How the % Sign Was Born
Medieval Italian merchants wrote 'per cento' (per hundred) so often that scribes began abbreviating it as 'p cento', then 'pc̄o'. By the 17th century, the lazy quill stroke had evolved into the elegant symbol we know today: a slash flanked by two tiny zeros — %.
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