What Is Ylapse
Ylapse.com (pronounced “elapse”) is a fast, accessible web app for precise date and time math. Use the Date Calculator to add or subtract years, months, weeks, or days from any start date, or switch to the Duration Calculator to find the exact time between two date-times down to seconds. For schedules that follow office hours, our business-day/Workday Calculator skips weekends and U.S. federal holidays, and our time-zone handling keeps cross-region plans accurate. If you’re searching for a “date calculator,” “add days to date,” “time between dates,” or “business days calculator,” you’re in the right place.
We built Ylapse to be quick and frictionless: clean, sleek, and modern UI, crisp inputs, and zero clutter. Everything updates instantly as you type, so you can validate deadlines, SLAs, net terms, production lead times, appointments, and travel plans without spreadsheets. It’s mobile-friendly, meeting accessibility best practices, so anyone can get reliable results fast.
Ylapse is engineered for accuracy (leap years, month-end rollovers, mixed units) and consistency across time zones, with a roadmap that adds more regional holiday sets and pro features. Whether you’re a planner, project manager, accountant, student, or small-business owner, Ylapse keeps your scheduling tight and your workflow focused. Try it now and make every timeline clear, confident, and correct.
How To Use Ylapse
Date Calculator
Use this tool to add or subtract time from a start date. Perfect for deadlines, lead times, shipping ETA’s, payment terms, and reminders.
Choose Start Date
Click the date field and pick your starting date.Select Operation
From Operation, choose Add time to date or Subtract time from date.Enter Time to Add/Subtract
Fill any combination of Years, Months, Weeks, Days. Leave fields at 0 if not needed.(Optional) Include Time
Toggle Include Time if you also want hours/minutes in the calculation.Read the Result
The Result panel shows the final date and highlights it on the calendar. Use Reset to clear.
Pro tips:
Handles leap years and month rollovers automatically.
Mix units (e.g., 6 weeks + 2 days) for precise date math.
Duration Calculator
Quickly calculate the exact time between two dates. Shown in days, hours, minutes, and seconds.
Set the Date Range
Choose a Start Date and an End Date.(Optional) Include Time
If your range includes times of day, enable time to see an exact breakdown to the second.Check the Duration
The Duration card instantly displays the total span (e.g., 1 day, plus 24 hours / 1,440 minutes / 86,400 seconds).Use the Controls
Use the swap/direction button to flip dates and the Reset icon to start over.
Pro tips:
Ideal for date difference, age/tenure, waiting periods, rental billing, or project elapsed time.
Combine with the Workday Calculator when you only care about business days.
Workday Calculator
Count or add business days while automatically skipping weekends and US federal holidays.
Choose Calculation Mode
Count Workdays: number of workdays between two dates.
Add Workdays: start on a date and add N workdays to get the finish date.
Set Dates (and Quantity if adding)
Enter Start Date (and End Date for counting). If adding, enter the number of workdays.Adjust Business Rules
In Business Rules, set your weekend pattern (Saturday, Sunday) and toggle Exclude holidays (US Federal) to match your policy.Include End Date (optional)
Turn on Include end date if your convention counts the final day.Review the Summary
See Workday Count, plus a breakdown of total days, weekends skipped, and holidays skipped.
Pro tips:
Perfect for business day calculator needs: SLAs, net-terms, manufacturing lead times, onboarding timelines, and compliance windows.
Switch from counting to adding to map schedules both backward and forward.
Results update instantly as you change rules, no guesswork.
FAQ
How do I add or subtract days, weeks, months, or years from a date?
Use the Date Calculator. Select a Start Date → choose Add time to date or Subtract time from date → enter any mix of Years, Months, Weeks, Days. The Result panel updates instantly and highlights the final date on the calendar. Ideal for adding days to dates, deadlines, and lead times.
How can I calculate the time between two dates (in days, hours, minutes, seconds)?
Open the Duration Calculator. Set a Start Date and an End Date. You’ll see the total duration in days plus a breakdown in hours, minutes, and seconds. Perfect for project timelines, age/tenure, and waiting periods.
How do I count business days between two dates (skip weekends and holidays)?
Use the Workday Calculator → Count Workdays. Enter Start and End dates. In Business Rules, keep Saturday/Sunday as weekends and toggle Exclude holidays (US Federal) if needed. Optionally enable Include end date. The result shows workdays plus weekends/holidays skipped.
How do I add a specific number of workdays to a date?
Switch the Workday Calculator to Add Workdays. Enter your Start Date and the number of workdays. Adjust Business Rules (weekend pattern, holidays). The tool returns the exact finish date. Great for SLAs, net 30 terms, and production schedules.
Does the calculator handle leap years, month lengths, and month-end rollovers?
Yes. Date math automatically accounts for leap years and varying month lengths. Example: adding one month to Jan 31 rolls to the correct end-of-month date. No manual fixes required.
Can I include time of day or time zones in my date math?
In the Date Calculator, toggle Include Time to add/subtract hours and minutes with your date. The Duration Calculator supports precise time spans. Ylapse uses your device time zone by default; for cross-time-zone workflows, enter local times consistently.
What’s the difference between inclusive and exclusive end dates?
Inclusive counting includes the end date; exclusive does not. In the Workday Calculator, use Include end date to match your policy. Example: counting workdays from Mon → Mon is 1 day inclusive, 0 exclusive.
Can I mix units like 6 weeks + 2 days or subtract 3 months?
Yes. The Date Calculator accepts any combination of units. Enter values for Years, Months, Weeks, and Days in one step. Useful when schedules are expressed in mixed lead times.
How are weekends and holidays handled in business-day calculations?
By default, Saturday and Sunday are weekends. Under Business Rules, you can change the weekend pattern and toggle Exclude holidays (US Federal). If your region differs, leave holidays off and rely on the weekend setting.
How do I switch calculators or reset quickly?
Use the top tabs. Date Calculator, Duration Calculator, Workday Calculator. To switch modes. Click the Reset icon in any panel to clear inputs and start fresh.