Save to external file real time refresh,time stamptimesta

Hi to all!

I have a question regarding time stamp. How correct is it? is it realiable to use an timestamp while testing the software? 

I have noticed that my code has some issues with regards of being a bit late, but I am not sure, is it an timestamp thats having an issue or my code

Is it possilbe that sometime the time stamp is not correctly written?