Alexa doesn't directly do timers for SmartHome devices like lights or switches. Routines can sort of do this now by inserting a 'Timer' to delay turning on/off a light, but it's more immediate. A routine could turn on your outside light, wait five minutes, then turn it off. But if you're looking for set times, i.e. turn outside light off at midnight, back on at 7am then you want to use the individual light's timer/schedule function. This would be accessed from the SmartHome manufacturers app/software.