TimeSync: the right clock and regional settings on point of sale PCs

This is a case study of TimeSync, a small Windows tool I built for the computers that run BKC Soft's point of sale software for fiscal cash registers. The tool keeps the clock and regional settings correct, because they decide how the program reads dates and amounts.

Client and context

BKC Soft makes software for fiscal cash registers. Besides the website, license portal and e-invoicing service I built for them, I also work as technical support at the company, so I set up computers for the registers myself, in the field. I built TimeSync in early 2026, in 5 days, to make exactly that job easier.

Problem

The point of sale program does not format dates and numbers itself; it relies on Windows settings. If a computer uses a period instead of a comma as the decimal separator, the same amount is read differently, with no error message. If the clock drifts, receipts carry the wrong time.

Older computers running Windows 7 cause the most trouble, because they often do not keep accurate time. Setting them up is slow too: date format, time format, decimal separator and thousands separator sit in different places in Control Panel, and each one has to be opened separately. Doing that on every new register computer, or over the phone with a user who does not know where to click, wastes time a tool can save.

Why one character matters

In Serbian format, one thousand two hundred thirty four dinars and fifty six para is written 1.234,56: the period separates thousands and the comma marks decimals. In English format the same amount is 1,234.56. If Windows on a register computer uses the English format while the program expects the Serbian one, the period and comma swap roles, and the amount can be read as something else entirely, with no error message. Dates work the same way: 03.04. is April 3 in one format and March 4 in another. That is why TimeSync sets these formats as well as the clock, and checks them continuously, not just on first run.

Constraints

The hardest part was changing the regional settings. Windows requires administrator rights for changes like that, so the rights had to be handled while keeping the tool a single file you just run.

The second constraint was the internet. Register computers are not always online, and a tool waiting for an NTP server must not hang or shut down when the network is gone. It has to wait and try again.

Solution

Exact time from an NTP server

TimeSync syncs the clock with an NTP server, a server that provides exact time over the internet. The server is picked from a list or entered by hand (rs.pool.ntp.org in the screenshot). You set the sync interval, the number of attempts, the pause between them and the minimum offset below which the clock is left alone, so a one second difference does not trigger a change.

Regional settings in one place

The Region tab holds every setting the point of sale program reads: the language and region code (sr-Latn-RS), short and long date formats (dd.MM.yyyy), short and long time formats (HH:mm), decimal separator, thousands separator, number of decimals, list separator and negative sign. Instead of several Control Panel windows, one screen and one Save button.

Monitoring that puts settings back

Settings are not applied once and forgotten. Every 30 minutes the tool checks whether anything has changed them and restores what the point of sale program expects.

System tray and start with Windows

TimeSync starts with Windows and runs in the system tray, next to the clock. The icon color shows the state: green when everything is fine, yellow while a sync is running, red on an error, such as no network. Hovering shows the current status, and a double click opens the settings.

It does not give up when the network is down

If a sync fails after the set number of attempts, the counter resets and the tool tries again after a full interval. It does not shut down or quietly stop doing the job it was started for.

What you set, tab by tab

Tab	What you set	Example from the screenshot
Time	NTP server, interval, attempts, pause, minimum offset	rs.pool.ntp.org, 60 min, 3 attempts, 10 s, 2 s
Region	language and region, date and time formats, number formats	sr-Latn-RS, dd.MM.yyyy, HH:mm, 2 decimals
General	start with Windows, regional settings monitoring, check interval	on, check every 30 min

Setting up a new computer

1. Copy one .exe file to the register computer.
2. On the Time tab, choose the NTP server; on the Region tab, the formats the program expects.
3. On the General tab, turn on start with Windows and regional settings monitoring.
4. After Save, the tool disappears into the system tray, and a green icon shows that everything is fine.

Doing the same by hand means going through several Windows dialogs on every computer. With TimeSync it is one screen, and the settings stay put even when something changes them.

Technologies and why

TimeSync is written in C# for Windows and ships as a single .exe file, with no installer. For a tool carried from one computer to the next, that is the fastest form: copy, run, configure. It needs no database, hosting or maintenance.

Together with the efakture.exe service, which connects the point of sale program to the e-invoicing system and e-delivery notes, TimeSync is the second Windows piece of my work for BKC Soft. The service sends the documents, and TimeSync keeps the settings that decide how the program reads dates and amounts.

Result

Installing and setting up a computer for a fiscal cash register is now quick: one file and one screen instead of a tour of Control Panel. The clock stays accurate even on older Windows 7 machines, and regional settings restore themselves if anything changes them. I do not know exactly how many computers run the tool, so I do not quote a number (as of October 2026).