This is pure curiosity on my behalf.
By way of background, I use Dimension4 to synch the time on my PC with my ISP's time-server and that seems to work fine for me and my PC. D4 offers a range of different time-servers, but you can only nominate one as your time-server.
I wondered, what if my chosen time-server is just a wee bit inaccurate? (Note1: if it is, the difference is probably of no consequence to me in my everyday usage. Note2: given Note1, what do I care? Note3: "wee bit inaccurate" is deliberately vague.)
Is there an app which will check a number of differing time-servers at the same instant and report back to the user what results it gets from each time-server? (If I was using this app, I would run it manually, probably no more frequently than once a month, at most.)