(What time is it?)
Wann findet der Vortrag statt?
(When is the presentation going to take place?)
(Do you know what time it is?)
Können Sie mir sagen, wann der Vortrag stattfindet?
(Can you tell me when the presentation is going to take place?)
Indirect yes/no-questions take "ob" ( = if, whether) as a subordinating conjunction.
(Did our neighbours buy a heat pump?)
(Can you tell me whether our neighbours bought a heat pump?)