I'm trying to remember off the top of my head, so I could be wrong, but I think there might be a scale option in the menus of the graph editor, or maybe I'm thinking of copy/paste... so two options

1) Select all your keys, grab the scale tool, MMB+Shift drag scaling the keys together (the Shift constrains it to changing the time and not the values too). This will probably result in keys being between/within? frames. Select some keys and check the frame at the top of the graph editor. It might say 12.645 or something. Select the keys again and move them to snap to keys (there's a snap function somewhere, I know).

2) Copy or cut (can you cut?) all the keys, then go edit > paste option box. There will be many confusing options on how/where to paste the keys. The default settings will probably work, but there should be an option to scale them in the paste settings.

Sorry, don't have maya here or I'd test it out, but either of those should give you what you want.