How do I get my date to match my attire?

[TheSimsMaster]

When you ask a sim on a date, you usually go in your casual clothing. Sometimes I want the date to be a bit more formal, so I have my sim change into formal clothing. When we arrive at the community lot, my sim's date is in casual. Is there a way to change him/her into the attire I want without cheating?   

[rwills]

A lot depends on how elastic your own definiton of "cheating" is*.

If making an unselected Sim selectable for a minuite or two and then changing his/her clothing or having him her use a dresser to change clothes or something along those lines (either at the comminity lot or by way of being invited to your own Sims' house first) falls under "cheating," then probably no,  in the sense of being sure of their attire beforehand.

However, if you don't consider it a cheat, there are some hacked objects which you can place on a lot or in a room (and in which the hack can be activated or deactivated at your discretion) which will force most Sims (some employees and NPCs may be excepted) into formal wear without first making an unselectable Sim selectable.

See here (scroll down a bit on both pages linked):

http://www.simlogical.com/sl/Sims2Pages/Sims2_Doors_ClothesChange.htm

http://www.simlogical.com/sl/Sims2Pages/Sims2_Dressing.htm

*EDIT for clarification: That is, if most hacks and mods fall under that label for you, as basically what they do is activate or allow to be activated cheats without having to type in the cheat code.

[mhbuck21]

Also, you might consider changing the classification for the specific outfit(s) to formal as well as casual, or even find a suitable casual outfit that looks the part. Then you can make the date wear it beforehand, making them selectable for a bit, just like rwillis suggests. They'll arrive in the outfit you chose for them. Anyway, that might be another way around it. I usually choose casual clothes that might serve as formal (cheaper too).
Mari