Free Date Calculator Calculate date durations, add or subtract days, find weekdays, and more. Select a calculation type below. Calculation Type: Count Days Add Days Subtract Days Workdays Add Workdays Weekday Week No Start Date: End Date: Calculate Days Start Date: Days to Add: Add Days Start Date: Days to Subtract: Subtract Days Start Date: End Date: Calculate Workdays Start Date: Workdays to Add: Add Workdays Date: Find Weekday Date: Find Week Number