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Date, deadline & cycle calculators

Turn dates into clear next steps.

Calculate dates, deadlines and recurring windows — with the assumptions and sources behind every result.

Search 184 calculators by question, topic or outcome.

Popular tasks Date differenceAdd or subtractBusiness daysHoursSleep timesDays until All 184
Example result Get the date. See the rule.

90 calendar days from an example date ·

Sunday

  • Start date excluded
  • Calendar days

Your device date and time zone load locally.

Calculation receiptRule and source shown beside the answer.

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Open Date Calculator Browse all 184 calculators
184CalculatorsAcross 53 real-life categories
No sign-upStart immediatelyNo account before an answer
Local-firstInputs stay hereSensitive values stay in your browser
Rules shownSources includedReview context beside the result
Start with a question

What are you trying to work out?

Choose a common task or describe your own question in the search above.

01

How many days are between two dates?

Compare calendar days, weeks and the counting convention used.

Open calculator 02

What date is 90 days from now?

Add or subtract days, weeks, months or years from a starting date.

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How many business days are there?

Count weekdays and apply the selected weekend and holiday calendar.

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How many hours are between two times?

Find elapsed hours and minutes, including overnight spans.

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What time should I go to bed?

Compare practical bedtime and wake-up windows with clear assumptions.

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How long until an event?

Build a live countdown and carry the target date into your calendar.

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The answer, with the rules attached

A date you can inspect.

CalcSpan shows what was counted, what was excluded and which source shaped the result.

See how CalcSpan works
  1. 01
    Answer first

    Get the date, duration or window immediately.

  2. 02
    Assumptions visible

    See inclusion rules, exclusions and regional context.

  3. 03
    Take it with you

    Copy the result, save an image or add the date to your calendar.

Browse by life area

Start with a category.

Explore a focused set first, or open all 53 categories when you need a more specific calculator.

39 Universal date, business-day and time calculations 4 tools 41 Countdowns, holidays and school calendars 6 tools 42 Time cards, payroll and leave planning 4 tools 45 Pregnancy, cycles and treatment planning 5 tools 02 Health, childcare and developmental milestones 7 tools 21 Jet lag, passports and travel rules 4 tools 01 Pets, reproduction and life stages 4 tools 18 Fermentation, baking and culinary aging 4 tools 43 Billing, contracts and financial dates 11 tools 47 Personal planning and renewal dates 10 tools 19 Photography, tides and astronomy 5 tools 40 Age, birthdays and life milestones 7 tools
View all 53 categories
03 Immigration, travel and employment notices 3 tools 04 Education entry and sports age groups 2 tools 05 Rent, housing and closing dates 3 tools 06 Court deadlines and legal procedure 2 tools 07 Gardening, planting and frost calendars 2 tools 08 Weddings, anniversaries and life planning 2 tools 09 Consumer product safety and shelf life 2 tools 10 Taxes, investments and holding periods 3 tools 11 Residency and immigration status 3 tools 12 Workplace leave and PTO 2 tools 13 Trials, subscriptions, returns and warranties 5 tools 14 Tattoos, aesthetics and recovery 3 tools 15 Recovery, habits and behavior change 3 tools 16 Drug half-life and metabolism 2 tools 17 Construction materials and DIY curing 3 tools 20 Vehicle maintenance and DMV timing 3 tools 23 Breast milk, feeding and replacement parts 3 tools 24 Aquariums, reptiles and equipment care 2 tools 25 Training cycles and recovery planning 7 tools 26 Camping, preparedness and emergency supplies 2 tools 27 Academic writing and research timelines 2 tools 28 Instrument strings and tuning care 2 tools 29 RV living and off-grid energy 2 tools 30 Lawn care, pests and septic maintenance 3 tools 31 Pilot duty and medical certificate timing 3 tools 32 Insurance claims and COBRA windows 3 tools 33 Drug-testing and exposure windows 2 tools 35 Horse, cattle and farm breeding 2 tools 36 Patents, trademarks and copyright terms 2 tools 37 Esports rank decay and battle passes 2 tools 38 Film processing and darkroom chemistry 2 tools 44 Tax residency and visa absence tracking 3 tools 46 Time zones, timestamps and date standards 5 tools 48 Education and academic planning 5 tools 49 Cross-border commerce and logistics 4 tools 50 Benefits and retirement deadlines 4 tools 51 Real estate and contract milestones 1 tools 52 Endurance training and race planning 3 tools 53 Animal incubation and reproductive care 2 tools 54 Fermentation and culinary science 3 tools 55 Professional licenses and continuing education 1 tools
All calculators

Browse the catalogue.

184 catalogued calculators across 53 real-life categories. Exact direct-mode and value-specific pages appear as the best route when your search calls for them.

18of 184 shown

Type a topic, then use Enter to open one clear match or move to the first result. Use the category and sort controls to refine the list. Results load from a compact index when you search.

Date Calculator

Measure date spans, add or subtract calendar units, count business days and compare date-times with explicit inclusion, holiday, time-zone and DST rules. Inputs stay in your browser.

Universal date, business-day and time calculationsCalculator

Hours Calculator

Find the exact hours and minutes between two clock times, including overnight spans and an optional break, without payroll assumptions. Inputs stay in your browser.

Universal date, business-day and time calculationsGuide + calculator

Days Until Calculator

Build a clear countdown to any target date with days, weeks and explicit endpoint counting. Inputs stay in your browser.

Countdowns, holidays and school calendarsCalculator

Sleep Calculator

Plan bedtime or wake-up ranges from NIH-described 80–100 minute sleep cycles without promising sleep quality, stages or medical outcomes. Sensitive inputs stay in your browser. Verify important decisions with a qualified professional.

Personal planning and renewal datesGuide + calculator

Age Calculator

Calculate exact calendar age, total elapsed days and the next birthday from a birth date and an as-of date. Inputs stay in your browser.

Age, birthdays and life milestonesCalculator

Time Card Calculator

Subtract an unpaid break from a same-day or overnight shift and estimate straight-time pay. Inputs stay in your browser.

Time cards, payroll and leave planningCalculator

Biweekly Pay Schedule Calculator

Generate every 14-day payday in a selected year from one known payroll anchor date. Inputs stay in your browser.

Time cards, payroll and leave planningCalculator

Meeting Time Planner

Convert a local meeting instant between searchable IANA time zones with DST gap and ambiguity handling. Inputs stay in your browser.

Time zones, timestamps and date standardsCalculator

Pregnancy Week Due Date Calculator

Estimate due date and gestational week from LMP or conception while preserving clinician dating authority. Sensitive inputs stay in your browser. Verify important decisions with a qualified professional.

Pregnancy, cycles and treatment planningGuide + calculator

Schengen 90 180 Calculator

Audit an unlimited travel ledger against every rolling Schengen 180-day window, estimate remaining days and earliest re-entry, and separately check shorter visa-sticker limits. Inputs stay in your browser.

Immigration, travel and employment noticesCalculator

Payment Terms Calculator

Calculate invoice due dates from invoice, receipt, acceptance or end-of-month anchors, then show overdue days, an AR aging bucket and a local reminder. Inputs stay in your browser.

Billing, contracts and financial datesCalculator

Flight Time Arrival Calculator

Convert an airport-specific itinerary duration into local arrival time, or label a great-circle duration clearly as a planning estimate. Inputs stay in your browser.

Jet lag, passports and travel rulesGuide + calculator

Minutes To Decimal Hours Calculator

Convert minutes to payroll-style decimal hours with selectable precision and a reverse-rounding check. Inputs stay in your browser.

Time cards, payroll and leave planningCalculator

Next Federal Holiday Calculator

Find the next observed U.S. federal holiday and distinguish it from employer, school and state calendars. Inputs stay in your browser.

Countdowns, holidays and school calendarsGuide + calculator

Cat Age To Human Years

Find the AAHA/AAFP feline life stage, next boundary and a clearly labeled human-age comparison. Inputs stay in your browser.

Pets, reproduction and life stagesCalculator

Dog Age To Human Years

Choose from 143 breed cohorts to estimate life stage, senior threshold and a human-age range, with a mixed-breed weight fallback. Inputs stay in your browser.

Pets, reproduction and life stagesCalculator

Dog Pregnancy Whelping Calculator

Use tested ovulation, an LH peak or a mating record to build the correct whelping range, veterinary imaging checkpoints and symptom override. Inputs stay in your browser.

Pets, reproduction and life stagesCalculator

Puppy Adult Weight Predictor

Project an adult-weight range from age, sex and a reviewed breed or size profile, with optional trend comparison. Inputs stay in your browser.

Pets, reproduction and life stagesCalculator
More calculators, A–Z — 166 links
Keep the dates that matter

Calculate it once. Keep the date close.

Save deadlines, recurring windows and milestones to this browser, then export calendar reminders when you need them.

Open My Spans How local storage works
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ThenCourse finish targetOct 12 · 45 minutes per day
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