Date Difference Calculator
Calculate days, weeks, months, and years between two dates. Perfect for planning events, tracking milestones, and project management.
Calculate Days Between Dates
A date difference calculator determines the exact number of days, weeks, months, and years between two dates. Essential for project management, event planning, tracking milestones, legal deadlines, pregnancy due dates, and personal goal tracking. Understanding time differences helps with scheduling, budgeting, and life planning.
Common Uses
Personal Planning
- Event countdowns: Days until wedding, vacation, birthday
- Relationship milestones: Dating anniversary, marriage anniversary
- Life goals: Days spent on diet, exercise routine, sobriety
- Pregnancy: Days until due date (typically 280 days from last period)
Professional Applications
- Project management: Project duration, milestone tracking
- Legal deadlines: Contract terms, statute of limitations
- Financial planning: Loan terms, investment holding periods
- HR/Payroll: Employee tenure, probation periods, benefits eligibility
Quick Reference
- 1 week = 7 days
- 1 month (average) = 30.44 days
- 1 year (average) = 365.25 days
- 1 decade = 3,652.5 days
- 1 century = 36,525 days
Common Time Periods
Business Timelines
- 90-day probation: 13 weeks
- 6-month review: ~26 weeks or 182 days
- 1-year contract: 365 days
- 18-month project: ~547 days
Academic Periods
- Semester: ~105 days (15 weeks)
- Quarter: ~70 days (10 weeks)
- School year: ~180 days (36 weeks)
- Bachelor's degree: ~1,460 days (4 years)
Pregnancy Timeline
- Full term: 280 days (40 weeks)
- First trimester: 0-13 weeks
- Second trimester: 14-27 weeks
- Third trimester: 28-40 weeks
- Premature: Before 37 weeks
Legal Time Periods
Statute of Limitations (varies by state/type)
- Personal injury: 2-6 years (730-2,190 days)
- Breach of contract: 3-6 years
- Debt collection: 3-10 years
- Property damage: 2-6 years
Waiting Periods
- Divorce (some states): 30-365 days
- Background check: 3-10 business days
- Notice to vacate rental: 30-60 days
- Two weeks notice: 14 days
Historical Time Calculations
Major Events Days Ago
- Y2K (Jan 1, 2000): ~9,000 days ago
- 9/11 (Sep 11, 2001): ~8,400 days ago
- 2008 Financial Crisis: ~6,000 days ago
- COVID-19 Pandemic start: ~1,750 days ago
Tips for Accurate Calculation
- Include vs exclude end date: Clarify if counting includes the final day
- Time zones: Same date can be different in different zones
- Leap years: Automatic in modern calculators
- Daylight saving: Doesn't affect date counts, only time
Calendar Quirks
- Not all months have same days: 28-31 days
- Leap year: Feb has 29 days every 4 years (except century years not divisible by 400)
- Year 2000 was leap year, 1900 was not
- Next non-leap century year: 2100
Project Management Tips
Adding Buffer Time
- Add 20% buffer for unknowns
- 90-day project → plan for 108 days
- Accounts for delays, holidays, sick days
Milestone Planning
- Break long projects into 30-60 day milestones
- Weekly check-ins for projects over 90 days
- Daily standups for sprints under 14 days
Planning Tip: When scheduling important events or deadlines, count backwards from the due date rather than forward from start date. This ensures you don't run out of time and helps identify if the timeline is realistic.