You are going to have to change the time on your DS or just wait for the right time...
If you are impatient to find 5 Mechanical Skills, here is a schedule for
finding them:
On Monday at 8.00 a.m. in the northwest corner of the Government Laboratory
On Monday at 4.00 p.m. at the shrine dedicated to Auda Sherif in Mamma Hogg's
bedroom
On Tuesday 12.01 a.m. in the blue corrugated carton in the Secret Warehouse
On Tuesday at 4.00 p.m. in the Furnace Room, above the pallet
On Wednesday at 4.00 p.m. in the Vault, above the pallet
On Thursday at 8.00 a.m. in the Furnace Room above the pallet
On Thursday at 4.00 p.m. next to the stairs in the Basement
On Friday at 12.01 a.m. in the Freezer
On Saturday at 12.01 a.m. in an alcove in the Atrium Centre
On Saturday 4.00 p.m. in the Government Laboratory
Here is a warning as well...
Turning the clock 'back' is particularly dangerous as it may
entirely ruin your game. Your Sim will behave in the same way as when 'zapped' by aliens or robots, and be drained of energy and unable to function at maximum level for DAYS. Moreover, if you move the clock forward more than a couple of times, that will ruin the game as well. Almost everything in this game is based on real time; to change the clock will confuse the programming.
I have gotten this information here.
Link