If you only want to move the age within a lifestage, then ambrosia is your best bet. Unfortunately, by the time that your sim can make it, she'll be dead.
Here's a mod which makes it fairly simple: requires a cooking skill of 1 with buyable life fruit and deathfish. Cheat your sim some money to buy the recipe and ingredients. I have used this mod and can vouch for it: http://www.simlogical.com/Sims3Tool....php?topic=71.0
Let's hope that EA realizes that people do not want to create a sim, only to find that s/he's been given only 1 day of adult life. Or, at least that some modder will find a way to set the number of days left in any stage.
If, you are interested in moving to a previous life stage (elder to adult, adult to teen, ...), then I believe that you are out of luck. From Pescado's awesomemod thread:
Originally Posted by Pescado
CONSOLE & DEBUG FEATURES:
6. "dresser [<SIM NAME>]", "mirror [<SIM NAME>]". Self-explanatory.
If no name is provided, will edit currently selected.
7. "editsim <SIM NAME>": As above. EXPERIMENTAL and UNSUPPORTED.
Can edit facial features and favorites. Do not attempt to change a sim's
weight, age, or traits using this command. No support will be provided
for this command: YOU ARE ON YOUR OWN!
As I understand it, the problem is that earlier life stages cannot have as many traits, so the game attempts to delete one or more of the traits. Unfortunately, it fails miserably and probably corrupts your game in the process.