I've been reading through the boards and it sounded like the only way to make it always daytime was to use hMods which now no longer works. I have check the properties file, and there was no option in there. It also appears that there is no command for it. Please help.
As far as I know this is only possible with some kind of client-side or server-side mod, it's not an option in survival mode, if you want to just build why not play Creative? and if you're fed up of :SSSS:'s blowing up your stuff, just turn the game difficulty to Peaceful, it'll still turn night but no enemies.
the way you change to creative is dependent upon if you have a world plugin and if so what one. if you only have 1 change it to creative in the server properties folder you should see gamemode make that creative/1 or if you have a plugin you would have to say what one or just find the command or go under the plugins configuration page