Any way to sync time with a PC without any extra software?

Win 7 PC with parental controls on my kids' accounts. When it's almost time for the accounts to be enabled, the kids are waiting anxiously to login. :) Because the wall clock is not exactly in sync with the PC, their first login attempts may fail.

I've found some software clocks for Win 7 that display time on the login screen, but they are of such dubious origin that it's probably wiser to not even touch them.

A perfect solution would be a small Arduino with a 7-segment LED display the size of a CD-ROM bay. The Arduino would get its time synced with the PC and display it. I know how to do everything, but I'm not satisfied with the time sync between Arduino and PC.

The Time library shows an example for sync-ing the time from PC to Arduino using a Processing sketch. This might ultimately work - I could configure the sketch to run every time the computer boots up and sync the Arduino this way.

Is there a simpler method? Does the USB protocol provide any way to read time from a USB host? I'm trying to find the simplest solution that would ensure the Arduino stays synced to the PC, using minimal hardware and as little software running on the PC as possible. I could use GPS, but that's extra hardware and it's not actually synced to the PC. I could use NTP, but that's extra hardware (Ethernet shield).

Any idea is welcome. Thanks!

Under any circumstance You will still need the Processing code to get your PC to talk to the external display. There is the Time Library.. Running on it's own processor it's accurate to within seconds/day. There are too, Various RTC modules. This one looked good enough to buy one, I'll get it in 2 weeks.. There is also a place to "Contact The Seller" that might be of use to you. I was impressed because next to Satellite GPS it's the most accurate module I've seen. GPS Time is very possible but a GPS module is about $22 - $24 dollars and they don't work very well inside. I am on the bottom floor of a 2 story Apartment building and It can take several hours to get enough data for a fix and for me at least Good Time, too. I think your best bet is this guy:

The Microchip MCP79412 RTCC offers several advantages over other low-cost real-time clocks. Among these are on-chip calibration, dual alarms, power fail/restore timestamps, 64-bit unique ID, 128 bytes EEPROM, 64 bytes battery-backed SRAM, 1.8-5.5V supply voltage, I2C clock frequency to 400kHz.

This From the Accurate Clock by our Own Jack Christensen.. ( My Emphasis )

Doc

That Microchip thing looks very good indeed. I’ll bookmark it, thanks.

I need to focus on ways to synchronize with the PC. I don’t need a clock that is very accurate per se, I just need a clock which is close to the PC clock, within a second or so. That’s the main requirement. The PC is normally synced to the worldwide NTP network, but I can’t always assume that.

Looks like I may have to figure out a way to send a clock sync from the PC at boot, and then maybe every hour or so. That ought to be good enough, I suppose.

Any idea is welcome. Thanks!

learn your kids to set the time of the wall clock right ;)

Opening up the com port and sending the timestamp from the pc... just choose your software pc side

I may have missed something(wouldn't be the first time), but I think that there's a way to have the computer update time over the internet automatically. So instead of the kids watching the clock on the wall, have them watch the time in the task bar of the CPU.

But it is fun to have a cool project to work on! :D

They can't login before the time is up, and Win 7 does not display any time information on the login screen. If it did, this project would not have started.

You can try thishttp://www.askvg.com/get-windows-8-like-date-and-time-display-on-windows-7-login-screen/