I haven't published my designs (at least not yet) but you are welcome to have any code that may be of interest to you.
Since most of the design effort for the radio time clock went into getting a usable radio signal against interference from (a) the display multiplexing (b) providing a stable power source and (c) switch mode power supply, this may not interest you since you have more or less excluded a radio time source.
All of the designs use a real time clock module as a basis and displaying the time from a real time clock module, on a 7 segment display or similar, is relatively simple (to a resolution of 1 second) and these are now dirt cheap (look for DS3231 in eBay). If you do it this way, you don't have to maintain the time yourself with say the time library or similar tricks and you don't have to provide an update interface (for DST or other corrections).
If you have power over Ethernet available where you want to site your main clock module, then it is a relatively simple task do design a clock, based on an RTC, which is occasionally corrected by contacting an NTP server. You have only to derive a local time from UTC. The only parameter you have to specify is the Network Time Server and you can probably get away with hard coding that in your sketch. Hardware requirements are an Arduino of your choice, an Ethernet module and an RTC. That is it.
The WLAN approach is a bit more complex because usually WLANs are protected and your WLAN module needs to be fed credentials (SSID, Password) to gain access. Here I could imagine a single button on the clock to force it into 'program' mode. In this mode, it's web server would publish a page where the user could enter the required WLAN credentials and, possibly, a choice of NTP server.