Date Calculator
Articles, guides, and in-depth tips for the Date Calculator — everything you need to get the most out of it.
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Why Legal Deadlines Are Harder to Calculate Than They Appear — Service Dates, Day Counting Rules, and Limitation Periods
Business Day Calculations: Why "30 Business Days" Is Approximately 6 Weeks — and Why the Exact Count Depends on Which Jurisdiction You're In
"Business day" isn't legally standardized — its meaning depends on whether you're counting bank days, stock exchange trading days, or standard Monday-Friday minus holidays in a specific jurisdiction. Here's why 30 business days is approximately 6 calendar weeks, the T+1/T+2 settlement convention for financial markets, why legal notice periods need both a jurisdiction and a "does the notice day count?" specification, and why public holiday calendars vary dramatically by region and year.
Week Numbering: Why January 1st Can Be "Week 1," "Week 52," or Something Else Entirely
January 1st can be "Week 1," "Week 52 of last year," or somewhere else entirely, depending on whether you're using ISO 8601 week numbering (Monday start, Week 1 = week containing January 4th) or the US convention (Sunday start, Week 1 = week containing January 1st). Here's how these conventions diverge, why some years have 53 ISO weeks, the ISO "week-based year" subtlety, and how spreadsheet WEEKNUM defaults can silently produce the wrong convention.
Day-Count Conventions: How Banks Calculate Days for Interest and Why Fiscal Years Differ
Banks use different day-count conventions (Actual/365, Actual/360, 30/360) that produce different interest amounts on the same deposit. Here's how these conventions work, why fiscal years differ by country, ISO 8601 week numbering, and the business days vs calendar days distinction in contracts.
Date Calculator — Calculate Exact Deadlines, Notice Periods & Milestones
Learn why date arithmetic is harder than it looks, the three core date calculation operations, and how to handle legal notice periods, contract milestones, visa limits, and medical schedules with a free date calculator.
Date Calculator — Add, Subtract & Find Days Between Dates
Learn how to calculate the number of days between two dates, add or subtract days from a date, and solve everyday date math problems instantly with a free date calculator.
Date Calculator — Find Days Between Dates or Add Days Instantly
Use the free date calculator on sadiqbd.com to find the difference between two dates or add and subtract days from any date — handles leap years, month lengths, and deadlines instantly.
