Toyota 2015 Prius Owner's Manual page 262

2-2. Instrument cluster
Selecting 12h/24h clock display
■
STEP 1
STEP 2
240
PRIUS_OM_OM47A17U_DVD_(U)
Select "CLOCK".
Press and hold the "DISP" button
to enter the setting mode.
Select "12h" or "24h".
Press and hold the "DISP" button
to finish setting.