Does my portal tell my customer what time they can check in and check out of the hotel?

Yes, in most cases those times are shown, but they come from the supplier and they are not always filled in for every property.

The check in and check out times sit in the hotel information that the supplier sends along with the rates, so your portal displays them on the hotel page and carries them onto the voucher your customer receives. Larger hotels and chains almost always provide them. Some small guest houses and apartments do not, and when the supplier sends nothing, your portal leaves the field blank rather than inventing a time. So a missing time is not a fault in the booking, it simply means the property has not published one.

It is also worth telling your customers that these are the hotel's standard times, not a promise about their own room. If somebody wants to arrive in the morning or stay on until the evening, that is a request the front desk decides on the day, and it may carry a charge set by the hotel. Adding it as a special request when booking helps, but it is not a guarantee, and nobody at your end can confirm it in advance.

Before you send the voucher, look at whether the times are actually there, and if the field is empty for a property your customer is arriving at late, contact the hotel directly and pass the answer on.