Time calculation by subtraction:

I made this device to calculate Hours ,Minutes , and seconds.
It can take an unformatted second count such as 256 and by subtraction find out how many minutes.

Here is how it would look like in code: pastebin link
To use the device click the button to add the scoreboard values, then use this command:

/scoreboard players (username) set seconds <value>

The larger the seconds value is, the longer it takes.

Just thought this may be somehow useful for you guys to have.

UPDATE:

• Added timer function
  
• Fixed bug where it wouldn't calculate seconds count under 60
  

UPDATE 2:

• Reduced size from 19W x 8L x 7H to 19W x 7L x 5H