Optional spoilers for everyone, pick only 1.
All of them have a chance to get a reduction, but some are more risky than others.
WARNING: May add up to 6 days, look at your own risk!
High risk:
Spoiler:
Flip a coin. Heads: Add 6 days, Tails: 12 day reduction.
Medium risk:
Spoiler:
Flip a coin. Heads: Add 4 days, Tails: 7 day reduction.
Low risk:
Spoiler:
Flip a coin. Heads: Add 2 days, Tails: 3 day reduction.
The more you gamble, the more you win.