Every 400 years, we skip three leap days
The Gregorian calendar drops leap days in years divisible by 100 but not 400—so 1700, 1800, and 1900 had no Feb 29, subtly shifting “days since” totals.
Calendar tuning
Time Since/Until Calculator
Quick Summary: Calculate the exact time between now and any date. Shows breakdown in years, months, weeks, days, hours, minutes, and seconds. Works for past dates (time since) and future dates (time until).
Pick a date/time
Tip: Press Enter in the field to calculate. The result updates to the second.
Result
Pick a date/time, then press Calculate.
About the Time Since/Until Calculator
This free tool lets you measure the exact amount of time between now and any chosen date/time, either in the past (since) or the future (until). It breaks the result into years, months, weeks, days, hours, minutes, and seconds, offering a clear and detailed picture of elapsed or remaining time.
The calculation is calendar-aware, meaning it accounts for the actual number of days in each month and leap years. This ensures that month and year counts match real-world dates instead of relying on rough day-based averages. The interface uses a built-in date/time picker for fast, accurate input, and the result updates instantly on click.
All computations happen entirely in your browser, using JavaScript to compare your selected date/time with your device’s clock. This guarantees privacy—your chosen dates are never uploaded to a server or stored anywhere online. Whether you’re tracking time since a milestone (birthday, project start, historical event) or counting down until an upcoming occasion (exam, launch day, anniversary), the tool works offline once loaded.
Common Time Calculations
This calculator handles various time measurement scenarios:
- Time since birth - Calculate your exact age in years, months, and days
- Days until event - Count down to birthdays, holidays, or deadlines
- Project duration - Track elapsed time since project start dates
- Historical dates - Find time elapsed since any historical event
- Anniversary calculator - See time since special milestones
Popular Uses
People use this calculator for everything from tracking how long they've been at their current job to counting down to retirement. Some calculate time since major life events—weddings, graduations, or the day they set to form new habits. Others track historical milestones: it's been over 55 years since the moon landing, for instance.
The tool works equally well for future dates. Planning a vacation in six months? Enter the date to see exactly how many weeks and days you have to save up.
Example: How Long Since January 1, 2020?
As of December 2025, it's been roughly 5 years and 11 months—or about 2,161 days. The exact count depends on the current time when you check. Enter the date above to see your live calculation.
Calculating Your Age
Most people only know their age in years, but this tool breaks it down further. Enter your birth date to see your age in years, months, weeks, days, hours, and even seconds. It's more accurate than a simple age calculator because it accounts for leap years and varying month lengths.
FAQs
How is it calendar-aware?
We step year-by-year and month-by-month from the earlier date to the later one. That respects real month lengths and leap years.
Does DST affect results?
No. Internally, the calculator works with UTC-equivalent timestamps derived from your local input, avoiding DST drift.
Can I share a prefilled link?
Yes—use Share link. It adds ?t=YYYY-MM-DDTHH:mm to the URL, which the page reads on load.
5 Fun Facts about Time Since/Until
Unix time is a huge number
Since Jan 1, 1970, more than 1.7 billion seconds have ticked by—great for “seconds since” bragging rights.
Epoch scale
UTC midnight avoids DST traps
Counting from midnight UTC dodges the one-hour “missing” or “double” hour of daylight saving, keeping durations consistent.
DST-proof
Weeks beat months for countdowns
“12 weeks” is always 84 days; “3 months” could be 90, 91, or 92—why countdown pros speak in weeks.
Planning hack
Your age in heartbeats
Roughly 115,000 beats per day means you rack up ~42 million beats a year—fun to pair with your “days since birth” number.
Body clock