Is there a Timeframe for rewardperiode

Maybe I’ve misread this part. Sorry if i’m asking the obvious.
I’ve got the message at the farming page: ’ Awaiting new rewards period’ .
Where can I find the information about the periods.
I’ve fount the excel document stating the weeknumbers and the amount of rewards.
But not the start-end of each period and the explanation of why there is the message ’ Awaiting new rewards period’ …

Hope someone can send me in the right direction or can share this information with me.