How to get current time and date in arduino without external source? I'm working on a project using Arduino Uno and SD card shield.
I'd like to store a variable at a specific time everyday in the SD card. How can I get the current time in Arduino ?
Any help would be appreciable.

NOTE : Arduino is NOT connected to PC.
An accurate enough way is to use the millis() function. It  will return the value in milliseconds since the start of the Arduino. If you start the Arduino at a specific time, you will be able to calculate the exact date and time.



Why not an external module?? An RTC such as the DS3231 in merely 5$ and it includes a temperature sensor for you!