How can I find out in advance when the extra challenger prize will be available for help wanted?

Upcoming Flash Bonus (red) Schedule for May-June 2025

May 11 @00:00UTC (May 10 @ 8pm EDT) to May 19 @23:00UTC (May 19 @ 7pm EDT)

May 20 @00:00UTC (May 19 @ 8pm EDT) to May 24 @23:00UTC (May 24 @ 7pm EDT)

May 25 @00:00UTC (May 24 @ 8pm EDT) to June 2 @23:00UTC (June 2 @ 7pm EDT)

June 3 @00:00UTC (June 2 @ 8pm EDT) to June 7 @23:00UTC (June 7 @ 7pm EDT)

June 8 @00:00UTC (June 7 @ 8pm EDT) to June 16 @23:00UTC (June 16 @ 7pm EDT)

June 17 @00:00UTC (June 16 @ 8pm EDT) to June 21 @23:00UTC (June 21 @ 7pm EDT)

June 22 @00:00UTC (June 21 @ 8pm EDT) to June 26 @23:59 UTC (June 26 @ 8pm EDT)

Extra Edition (green) Bonus Schedule for May 2025, starting 00:00 UTC for 24 hours

23rd @00:00UTC (22rd @8pm EDT)

30th @00:00UTC (29rd @8pm EDT)