Business & IT Date Calculator

CyprNet DeltaCalc is a precision date and time calculator built for answers you can understand, verify, and explain.

Calculate differences between dates, work with BCE/CE historical dates, count business days and holidays, create countdowns, convert Unix timestamps, calculate ISO dates, and round timesheets.

DeltaCalc is a calculator—not a calendar, reminder, or task manager. Your calculations stay on your device.

Free calculators

Between Two Dates/Times
Calculate calendar years, months, and days plus total weeks, days, hours, minutes, and seconds.

Historical BCE/CE Dates
Calculate date differences and add or subtract calendar offsets across BCE and CE dates.

Add / Subtract Date & Time
Add or subtract years, months, weeks, days, hours, or minutes from a date and time.

Countdown
Create live in-app countdowns for retirement, events, milestones, vacations, launches, birthdays, and more.

Business Days
Calculate working days using Saturday–Sunday or Friday–Saturday weekends, with built-in holiday calendars for:

United States Federal holidays
England & Wales
Canada

Unix Epoch Converter
Convert Unix epoch timestamps to local dates and times.

TLS Certificate Dates
Calculate certificate issue, renewal, and expiration schedules using TLS certificate timing rules.

ISO Date
See ISO week, ISO year, quarter, day-of-year, and related calendar information.

Timesheet Rounding
Round clock-in and clock-out times using 5, 6, 10, 15, or 30-minute increments with nearest, up, or down rules.

Pro calculators

A one-time Pro unlock adds advanced tools:

Lease Term
Notice Window
Proration
Installment Dates
TTL & Cache Expiration
SLA Availability / Downtime
Maintenance Windows
Log Timestamp Conversion
Shifts & Overtime
Advanced Timesheet Rounding
Time Accounting
Age & Tenure
Recurring Events
Sprint & Release Dates
Fiscal Calendars, including 4-4-5

Pro history and saved work

Pro also adds:

Up to 50 persisted history entries
Up to 20 named reusable scenarios
Favorite calculators
CSV export
JSON export
XML export

Free users can still keep the five most recent calculations during the current session and share individual results.

Designed for privacy

DeltaCalc performs calculations locally on your Android device.

No ads
No subscriptions
No analytics SDKs
No accounts
No cloud calculation service
No calendar access
No GPS tracking
No background alarms
No notification spam

One-time Pro unlock

Unlock all Pro features with a $0.99 purchase.

No recurring fee.

Restore your purchase automatically with the same Google Play account, or use Settings → Restore purchases.

Useful for

DeltaCalc is designed for anyone who regularly works with dates and times, including:

IT and DevOps
Network administrators
Project managers
Consultants
Legal and contract workflows
Payroll and workforce calculations
Business operations
Students and researchers
Historical date calculations
Everyday planning

Whether you need to know how many business days remain before a deadline, when a TLS certificate should be renewed, how long until retirement, how old a historical date is, or exactly how much downtime a service-level target allows, DeltaCalc gives you the math without turning the calculation into another calendar or subscription service.

CyprNet DeltaCalc
Precision date and time math—local, private, and explainable.

What's new — Version 1.0.7

DeltaCalc 1.0.7 greatly expands the calculator set.

New:

Countdown, including retirement and event countdowns
BCE/CE historical date calculations
Business-day calculations with US, England & Wales, and Canada holiday calendars
TLS certificate date calculations
ISO date information
Timesheet rounding
Recurring events
Sprint and release dates
Fiscal calendars
Time accounting
Advanced rounding

Also improved:

Pro history now survives restart
Up to 20 named Pro scenarios
Pro favorites persist

Still one-time Pro. No ads. No subscriptions. No calendar sync.