I don't mean the clock line I mean a normal clock with hours and minutes and days though I want to do other sort of things like gathering sensor data so I don't want it to take a lot of storage or time rather if it runs in the background I don't know what to do.the modules are expensive as well they're accurate but I don't want any thing more accurate than a second for my watch any library or thing?Tnx.
Edit:I'm sorry sending emoji looks like to cut the rest of the text and disappear it in your forum I used one of my keyboard emojis
Description of what you want to do is unclear; it sounds like you want to make a clock with arduino?
The Arduino itself is unable to keep time particularly well - it's accurate to a percent or two, so it'll lose seconds-to-a-minute per day (per spec on resonator - unfortunately they didn't use a more accurate crystal for the system clock). You can get an RTC clock module that keeps good time very cheaply, though (DS1302, DS1307 or DS3231 are the commonly used ones - they're about $1~2 each in an assembled module on ebay shipped from china via ox cart, $3-5 shipped within USA, and take a coin cell battery so they keep time with power off).
Making a clock with Arduino is a very common project; you can find lots of information via google.
Tnx for the reply nice RTC clock module are about 3 dollars in my country which is fine.The question about the battery on it, is can does it use the battery if it's connected to arduino?I just want it use its battery in case the arduino runs out of battery.Anyway its just a clock module it would work on so much less battery even when the main battery can't keep arduino on it still should turn the clock up am I wrong?