Time and duration to meditate I think I somewhere read that the Buddha said that when you meditate (on breath) for 30 minutes in the morning and in the evening, you will be accompanied by happiness and peace throughout the day. Is that true and if yes, can you tell me the sutra? Thank you!
There are three considerations: getting into meditation, establishing connection with (whatever it's called), and maintaining connection.

First, to get into meditation you need to be careful not to scare yourself. If you start too rough on yourself you may end up secretly hating it. So all my teachers always said, start gentle and enjoy, little by little. Maybe 15 mins at a time, once a day. Then maybe 20.

Second, to establish connection with (I still don't know what it's called, but you'll know it once you get there), you need to have a good long meditation session. Maybe 90 minutes. Something like this. This is how long it takes to actually get deep. You don't need to have every meditation session be that long, only when you really feel like it. But it is important to do it a few times, until you catch the right feeling (state? mood?) 

Then, once you have it, and feel it remain with you even in postmeditation, you need to maintain it. This typically takes about 30 mins twice a day. Or 45-60 mins once in the morning. Something like this. 

These are my numbers. Everyone is different, so I'm sure a bunch of people here will have different opinions. But here it is anyway.