Lifehacker has written about a very useful gadget – Days Since which keeps track of the days since a particular day. All you have to enter the number of days since that day and from now on, it will be calculating the days.
What about keeping track of days since your birthday. OK, now how to calculate days since your birthday till now? You can go to easycalculation.com for calculating days since a particular date.
Here is how my Days Since gadget looks like –
Digits courtesy 8085 :D!