27-02-11-53-08-18
We can play with bitcoin's blockchain and the last two digits of the number of transactions in a block (from 00 to 99; one chance in a hundred)
There are 2016 blocks/14 days --> ~1008 blocks/week
The last block is Block
#440843 (2016-11-27 16:20:24 UT) and it has 2198 transactions
For example: the players try to guess the last two digits of the number of transactions in Block #441850 (next Sunday 2016-12-04)
They can only play until Saturday 2016-12-03 23:59:59 UT
If nobody guesses the right number, the winner is the closest one without exceeding