This is a small and simple addon, all it does is remove the existing small clock from below the minimap, and instead replaces the text in the titlebar with a clock which has hours, minutes and seconds. The clock uses your local time and by default a 24-hour timestamp (which can be changed in the configuration). Hovering over the title bar will in addition to displaying zone information like you usually would expect also show today's date.
The only available configuration is in the .lua-file (open minimapclock.lua in the Interface/AddOns/MinimapClock folder, and change the first few lines accordingly. You can change to using a 12-hour format by changing
local use24hformat = true
to
local use24hformat = false