ISO Week Number & Week Calendar
Get the ISO week number for any date and browse the Monday–Sunday calendar.
⚡ Fast • 🔒 Private • ✅ Accurate
Daydelta — Fast online calculators & handy tools
Clean, lightweight, and built for speed. No frameworks, no trackers — just instant answers that work anywhere. We’ll add fresh tools weekly.
Latest tools
Age Calculator
Enter a birth date to get exact age in years, months, days — plus next birthday and weekday insights.
Days Between Dates
Calculate total days, weeks, months, and optional business days between two dates. Time fields supported.
Countdown
Create a live countdown to any date/time with time-zone control (local, UTC, or fixed UTC offset) and a shareable link.
Mail Delivery Time (ZIP to ZIP)
Estimate USPS delivery time by ZIP pair and mail class. Weekends & US holidays handled.
Significant Figures Calculator
Count significant digits and see why each digit is (or isn’t) significant.
Tool categories
We’ll populate these as each tool goes live.
📅 Date & Time
Age, days between dates, ISO week, countdown, time zones.
➗ Math & Percentage
Percentage change, percent of, quick math helpers.
💰 Finance
Loan payments, savings growth, currency converter.
🔁 Converters
Length, area, volume, temperature — metric & imperial.
🏃 Health
BMI, BMR & TDEE estimators (educational only).
🔧 Text & Utility
Case/slug converter, word counter, QR generator.
Coming soon
Week 1
- Age Calculator
- ISO Week Number & Week Calendar
- Percentage Calculator
Week 2
- Time Zone Converter
- Days Between Dates
- Countdown to Date/Time
Week 3
- Unit Converter (core)
- Loan Payment Calculator
- QR Code Generator
Why choose Daydelta?
⚡ Blazing fast
No frameworks. Minimal JavaScript. Optimized for Core Web Vitals.
🔒 Privacy-friendly
No unnecessary cookies or tracking. Calculations run in your browser.
✅ Transparent & accurate
We show formulas or logic, with examples and edge-case notes.
🌍 Works everywhere
Responsive layout, accessible controls, and support for multiple formats.
About this project
Daydelta offers a growing collection of simple, reliable calculators and small web tools. The goal is to keep things fast and distraction-free: clear inputs, instant results, and short explanations of how each result is computed. As we ship new tools, this homepage will update with direct links and brief descriptions so you can jump right in.
Disclaimer: All tools are for informational and educational purposes only and do not constitute financial, medical, or professional advice.