Webpage to calculate differences in time.

I download video from many different DVR systems as requested. Often times the DVR time is off, sometimes by a little, sometimes by many days and hours. An example of this would be that it is currently 5/18/18 3:00 PM and when look at the DVR time it may show 5/17/18 9:00 PM. So the system time is off quit a bit. Here is what I am looking to have a webpage do: 1) be able to enter the current date and time 2) In another field, enter the DVR system date and time 3) I would like the webpage to calculate the time difference and display with a "+" or "-" sign (or the words "Fast' or "Slow" in front of difference to show whether the calculated time between the DVR and actual time is fast or slow : -1 day, 3 hours, 11 minutes. 4) In another field I would like to be able to enter a specific time and the web page would then display the time that I need to search for on the DVR system time. Noting fancy, just numerical results. I have attached a screen shot and an excel sheet to show a sample layout. I am not familiar with the best format to make the requested calculations (PHP, Java, Etc...) so what ever works is fine. I need the project completed to be able to simply upload to my existing website and it will function as described. Basically there are two calculations that need to be made here. Please make sure that you fully understand this project before bidding on it. Thank you Andrew