Resources

Time, Dates & Global Scheduling

Expert guides on time zone coordination, date calculations, visa tracking, and international scheduling — from the team at timeandcal.

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Time Zones
How to Schedule Meetings Across Time Zones: The Complete Guide
Eliminate scheduling friction for good. A systematic framework for finding overlap windows across any number of global cities.
12 min read →
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Time Zones
GMT vs UTC: What's the Difference and Why Does It Matter?
They look identical in daily life — but GMT and UTC are fundamentally different. Here's what separates them and when it actually matters.
8 min read →
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Time Zones
Does Dubai Observe Daylight Saving Time? (And Other Countries That Don't)
Dubai stays at UTC+4 year-round. Here's why — and how it shifts the time gap with London and New York depending on the season.
9 min read →
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Time Zones
The Best World Clock Apps and Websites Compared (2026)
A head-to-head review of the leading world clock tools available in 2026 — timeandcal, World Time Buddy, Time.is, and more.
7 min read →
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Travel
How to Calculate Visa Validity: A Step-by-Step Guide
The Day 1 rule, the Schengen 90/180 rolling window, and the overlap trap — everything you need to calculate your last legal day without error.
11 min read →
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Date Calculators
How Many Days Until [Holiday]? How to Use a Date Calculator
Christmas, Eid, Diwali, New Year's — how to calculate exact countdowns to any fixed or moveable holiday, with and without a calculator.
7 min read →
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Date Calculators
How to Calculate Your Exact Age in Days
Have you passed your 10,000th day? A step-by-step manual method and the fast way to find out your exact day count — including leap year adjustments.
8 min read →
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Date Calculators
Leap Year Rules: Every Year Divisible by 4 Isn't Actually a Leap Year
The rule most people learned in school is incomplete. The real Gregorian system has three parts — and 1900 and 2100 are the proof.
8 min read →
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Date Calculators
How to Calculate Project Deadlines Without Getting Tripped Up by Month Lengths
Month-based milestones are unreliable. Here's how to use absolute day counts to set deadlines that don't shift when February shows up.
9 min read →
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Remote Work
Managing Remote Teams Across Time Zones: Tools and Strategies
From overlap windows to async-first frameworks and rotating meeting burdens — a complete operational guide for distributed team leads.
13 min read →
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Date Calc
How Insurers Price Risk to the Exact Day
Life insurance is priced to the exact day. One day younger at policy issue can save hundreds per year. Here is the actuarial math behind it.
10 min read →
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Time Zones
How Airlines Schedule Across Time Zones
Airlines run on UTC but sell local-time tickets and calculate fuel in block hours. Here is how ops teams reconcile three different clocks.
11 min read →
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Time Zones
Why Atomic Clocks Need Leap Seconds
Earth orbits the sun in 365.2422 days, not 365. That fraction forces leap years; irregular rotation forces leap seconds. The full picture.
9 min read →
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Time Zones
Async SLA Windows for Global Support Teams
Zero business-hour overlap between NY and Manila breaks live SLAs. Here is how to build tiered async windows that keep global SLAs intact.
12 min read →
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Date Calc
Business Days vs Calendar Days Explained
A 5-business-day SLA can mean 5, 7 or 9 calendar days depending on which country's holidays apply. Here is how global support teams handle it.
9 min read →
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Date Calc
Why 2100 Is Not a Leap Year
Every 4 years is a leap year — except centuries, unless divisible by 400. Here is the 3-rule system and the solar drift that requires it.
8 min read →
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Date Calc
Day Zero vs Day One: Legal Deadline Counting
Does a 30-day notice period include today? Courts and insurers differ. Learn the inclusive vs exclusive counting standards that determine deadlines.
9 min read →
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Time Zones
Fractional Time Zones: India, Nepal & Iran
Why India (UTC+5:30) and Nepal (UTC+5:45) use half-hour offsets. Learn the history behind fractional time zones and how to handle them in code.
8 min read →
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Time Zones
France Has the Most Time Zones Worldwide
France spans 12 time zones — more than Russia or the USA. From Tahiti (UTC−10) to Wallis & Futuna (UTC+12): the world's widest empire.
10 min read →
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Date Calc
How Many Days Old Am I? Day Milestones
Most people know their age in years, not days. Hitting 10,000 days is a milestone most miss. Calculate your exact day age and find your next milestone.
7 min read →
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Time Zones
International Date Line Explained
Fly west across the Pacific and lose a full day. Fly east and land before you departed. Here is how the International Date Line actually works.
9 min read →
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Date Calc
Why Ramadan & Chinese New Year Shift Annually
Ramadan shifts 10–11 days earlier each Gregorian year. Chinese New Year lands differently every time. Here is the astronomy behind both calendars.
10 min read →
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Time Zones
ISO 8601 vs RFC 3339: Timestamp Guide
ISO 8601 and RFC 3339 differ in ways that break APIs. A practical guide for engineers on exact syntax differences and when each standard applies.
11 min read →
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Date Calc
The 11 Days That Vanished in 1752
In 1752 Britain went to bed on Sept 2nd and woke on Sept 14th. Learn why the Julian calendar drifted and what those 11 missing days actually meant.
9 min read →
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Date Calc
Neonatal Age in Days: Medical Day Counting
A newborn's age in days sets drug doses and NICU thresholds. Learn why neonatal medicine counts in days — rounding to weeks can be dangerous.
9 min read →
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Travel
Schengen 90/180-Day Rule: Exact Calculation
The Schengen 90-in-180 rolling window catches thousands with overstay fines yearly. Get the exact method to calculate your remaining Schengen days.
10 min read →
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Time Zones
Social Jetlag: How Time Zones Harm Health
Social jetlag — the gap between your body clock and schedule — affects 70% of people. It raises metabolic risk and impairs cognitive performance.
10 min read →
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Date Calc
The 2038 Problem: Unix Epoch Overflow
On Jan 19, 2038, 32-bit Unix clocks overflow and reset to 1901. Learn which systems are at risk, what Y2K38 means, and how to future-proof your code.
10 min read →
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Time Zones
Why Databases Must Store UTC, Not Local Time
Local timestamps corrupt when servers migrate or DST shifts. Learn why every serious DBA stores UTC — and the real-world bugs that happen when they don't.
10 min read →
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Time Zones
Zombie Time Zones: Antarctica & the ISS
At the South Pole all time zones converge. On the ISS the sun rises 16 times daily. Here is how scientists manage time where geography breaks down.
9 min read →