The answer provided by Maximus is no longer valid for cmder 1.3+
You have to create a .lua file (for ex. my_prompt.lua) inside your cmder config folder with your customized definition (source).
Below my customization:
function custom_prompt()
cwd = clink.get_cwd()
prompt = "\x1b[1;32;40m{cwd} {git}{hg} \n\x1b[1;30;40m{time}\n{lamb} \x1b[0m"
new_value = string.gsub(prompt, "{cwd}", cwd)
add_time = string.gsub(new_value, "{time}", os.date("%x - %X"))
clink.prompt.value = string.gsub(add_time, "{lamb}", "λ")
end
clink.prompt.register_filter(custom_prompt, 1)
And this is the resulting prompt
C:\
03/25/17 - 20:56:14
λ
You can find more customization options for the time output in the Lua manual
update for comment reported error
function time_prompt()
os.setlocale ("", "time")
local cwd = clink.get_cwd()
local prompt = "\x1b[1;32m{cwd} {git}{hg} \n\x1b[30m{time}\n{lamb} \x1b[0m"
local new_value = string.gsub(prompt, "{cwd}", cwd)
local add_time = string.gsub(new_value, "{time}", os.date("%x - %X"))
clink.prompt.value = string.gsub(add_time, "{lamb}", "λ")
end