An easy to use date time calculator, currently provide these functions:

1. Date Difference: How many days between two date?
Example usage:
a. Calculate days or working days till the next important day, like next birthday or a holiday!
b. Calculate days you have lived! Just enter your birthday and today's date.

2. Date Add/Subtraction: What's the date after X days and Y weeks?
Example usage:
a. Something big is coming in 6 weeks, but what day would that be? this date calculator can tell you.
b. A task will take 22 working days, with this calculator you will know the target date easily.

3. Day Info: tells you the week day, days left for the year and the week number it belongs to.

4. Week number: shows the specified week number's start date and end date.