1. What is Anniversary Calculator?

The Anniversary Calculator calculates how many full years have passed between a given date and today. It's useful for tracking anniversaries, service years, or any important milestones.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• Today — Current date
• Anniversary Date — The reference date to compare with today
• 365.25 — Accounts for leap years (average days per year)
• floor() — Rounds down to the nearest whole number

Explanation: The calculation accounts for the exact number of days between dates and converts them to years, accounting for leap years by using 365.25 days per year on average.

3. Importance of Anniversary Calculation

Details: Accurate anniversary calculation is important for celebrating milestones, tracking employment years, calculating service benefits, and commemorating important events.

4. Using the Calculator

Tips: Simply enter the anniversary date (past or future) and click calculate. The calculator will show how many full years have passed (or will pass) between that date and today.

5. Frequently Asked Questions (FAQ)

Q1: Why use 365.25 instead of 365?
A: Using 365.25 accounts for leap years (which add an extra day every 4 years), making the calculation more accurate over long periods.

Q2: How is this different from just subtracting years?
A: Simple year subtraction doesn't account for whether the anniversary date has passed yet this year. This method calculates exact completed years.

Q3: Can I calculate future anniversaries?
A: Yes, the calculator works for future dates too, showing how many years it will be until that date arrives.

Q4: What's the maximum date range this can handle?
A: The calculator can handle any date within the range supported by PHP's DateTime class (typically years 100-9999).

Q5: Why does it sometimes show one year less than expected?
A: This happens when the anniversary date hasn't occurred yet this year. The calculator only counts complete years that have passed.