Two quick date tools in one. Days between dates: pick a start and end date to see how many days and weeks apart they are, useful for countdowns, deadlines, age in days, or how long since an event. Add days to a date: enter a start date and a number of days (use a negative number to go back) to find the resulting date, handy for “30 days from today” return windows, notice periods or medication schedules. Press “Today” to fill in the current date. Dates are counted by calendar days, ignoring time of day and time zones.
How it works: Both dates are converted to midnight UTC and the difference is divided by 86,400,000 ms (one day), so daylight-saving changes never cause off-by-one errors. “Approx. months” uses 30.44 days per month. Adding days uses the calendar, so month lengths and leap years are handled automatically.