日付計算ツール
日付間の日数を数えるか、時間を加減算
出典と方法論
Days Between = End Date - Start DateCalendar day calculation
How to Use the Date Calculator
Calculate the number of days between two dates or find a date by adding or subtracting days from a starting date. Perfect for planning events, tracking deadlines, or calculating age.
Two Calculation Modes
- Days Between Dates: Find the exact number of days, weeks, months, and years between any two dates
- Add/Subtract Days: Calculate a future or past date by adding or subtracting a specific number of days
Common Uses
- Calculate days until an event (wedding, vacation, deadline)
- Determine how long since a past event
- Find payment due dates
- Calculate project timelines
- Track pregnancy milestones
Quick Reference
Common time periods: 7 days = 1 week, 30 days ≈ 1 month, 90 days ≈ 3 months (quarter), 365 days = 1 year (366 in leap years).
Related Time & Planning Calculators
Plan loan payoffs using our amortization calculator to see payment schedules by date. Track retirement timeline based on your target date. Calculate grade deadlines for students. See how investments grow over specific time periods.
よくある質問
Enter both dates in our calculator for exact count. For manual calculation, count full months (using 30 or 31 as appropriate), add remaining days. Remember February has 28 days (29 in leap years). Our calculator accounts for all variations.
Enter your starting date and the number of days to add. For example, 90 days from January 15, 2024 is April 14, 2024. Our calculator handles month boundaries and leap years automatically.
Calculate total days between dates, then divide by 7. From March 1 to December 25 is 299 days or about 42 weeks and 5 days. Our calculator shows results in days, weeks, months, and years.
Business days exclude weekends and holidays. Count total days, subtract Saturdays and Sundays (approximately 2 per week), then subtract any holidays. Our calculator can optionally exclude weekends for business day calculations.
Enter your birth date and today date. Someone born on January 1, 2000 is about 8,760 days old on January 1, 2024. This fun calculation shows how many days you have been alive.
Our calculator shows the day of the week for any date. Historical dates and future dates work equally well. July 4, 1776 was a Thursday; December 25, 2030 will be a Wednesday.
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