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The Date Calculator provides two powerful modes for working with dates: calculating the difference between two dates, and adding or subtracting time periods from a date.

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Overview

Date Calculator offers the difference between two dates, as well as the ability to add/subtract years, months, and/or days to/from a given input date. Source Reference: src/Calculator/Views/DateCalculator.xaml.cs

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Calculation Modes

Date Difference

Calculate the time span between two dates in years, months, weeks, and days.

Add/Subtract Dates

Add or subtract a specific time period from a given date.

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Date Difference Mode

Calculate the exact difference between two dates.

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Features

  • From Date - Starting date
  • To Date - Ending date
  • Automatic Calculation - Results update as you change dates

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Result Display

The calculator shows the difference in multiple formats:
  • Years, Months, Days - e.g., “2 years, 3 months, 15 days”
  • Total Days - Total number of days between the dates
  • Total Weeks - Total number of weeks (with remaining days)
This multi-format display helps you understand the time difference in the most relevant units for your needs. Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:107-133

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Add/Subtract Mode

Add or subtract a time period from a specific date.

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Input Fields

  • Start Date - The base date for calculation
  • Years - Number of years to add/subtract
  • Months - Number of months to add/subtract
  • Days - Number of days to add/subtract
  • Add/Subtract Toggle - Choose whether to add or subtract the period

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Calculation

The result updates automatically as you adjust the offset values. You can combine years, months, and days in a single calculation. Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:135-157
Date calculations respect calendar system rules, including leap years and varying month lengths.

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Calendar Support

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Multiple Calendar Systems

The Date Calculator supports various calendar systems based on your Windows settings:
  • Gregorian Calendar
  • Hebrew Calendar
  • Hijri Calendar
  • Japanese Calendar
  • Korean Calendar
  • Taiwan Calendar
  • Thai Calendar
  • And more
The calendar system is automatically selected based on your regional settings. Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:33-34

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Localization Features

  • First Day of Week - Respects regional settings (Sunday or Monday)
  • Date Format - Uses locale-specific date formatting
  • Language - Displays in your system language
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:36-45

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Date Range

The Date Calculator supports dates within the following range:
  • Minimum Date: January 1, 1601 (Gregorian)
  • Maximum Date: December 31, 2550
The maximum year is set to 2550 due to CalendarDatePicker control limitations. Future updates may extend this range.
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:249-250

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User Interface

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Calendar Picker

  • Interactive calendar view for selecting dates
  • Click to select, or type dates directly
  • Keyboard navigation support
  • Touch-optimized for tablet devices

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Context Menu

Right-click on results to:
  • Copy - Copy the calculated result to clipboard
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:159-164

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Accessibility

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Screen Reader Support

  • Automatic announcements when results change
  • Live region updates for dynamic content
  • Descriptive automation names for all controls
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:233-238

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Keyboard Navigation

  • Tab - Navigate between fields
  • Arrow keys - Navigate calendar
  • Enter - Confirm date selection
  • Esc - Close calendar picker

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Data Persistence

The Date Calculator maintains state when switching between modes:
  • The “From Date” field persists when switching between Date Difference and Add/Subtract modes
  • Previously entered values are retained when returning to Date Calculator
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:170-194

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Usage Telemetry

The calculator logs anonymous usage data (in retail builds) to help improve the feature:
  • Which mode is used (Difference vs Add/Subtract)
  • Frequency of calculations
  • No actual date values are collected
Source Reference: src/Calculator/Views/DateCalculator.xaml.cs:113-156

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Common Use Cases

  • Age calculations - Calculate exact age from birthdate
  • Project planning - Determine project duration or end dates
  • Event planning - Calculate days until/since an event
  • Financial planning - Calculate payment periods and maturity dates
  • Historical research - Calculate time spans between historical events
  • Travel planning - Calculate trip durations and return dates

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