1. What is 90 Days Back Calculator?

This calculator helps you determine the date that was 90 days before a given date, with an approximate conversion to months for easier understanding in monthly contexts.

2. How Does the Calculator Work?

The calculator uses simple date arithmetic:

And approximates months as:

Explanation: The calculation accounts for exact calendar days, while the month conversion is approximate (assuming 30-day months).

3. Importance of Date Calculation

Details: Calculating dates 90 days back is useful for financial quarters, medication schedules, legal deadlines, and various business processes that operate on 90-day cycles.

4. Using the Calculator

Tips: Enter any valid date in YYYY-MM-DD format. The calculator will show the date 90 days prior and the approximate equivalent in months.

5. Frequently Asked Questions (FAQ)

Q1: Is the month calculation exact?
A: No, it's an approximation (90 days ≈ 3 months). Actual months may vary slightly due to varying month lengths.

Q2: Does this account for leap years?
A: Yes, the date calculation accounts for leap years, but the month approximation doesn't consider them.

Q3: Can I use this for business day calculations?
A: This calculates calendar days. For business days (excluding weekends/holidays), you'd need a different calculator.

Q4: What's the maximum/minimum date I can enter?
A: The calculator works with any valid date from 1970 to 2038 on most systems.

Q5: Can I calculate other day intervals?
A: This calculator is specifically for 90 days. For other intervals, you'd need to modify the code.