A 15 minute speed up is an item in Evony TKR (The King's Return).
The description of 15 Minute Speed Up in Evony TKR says:
Reduces remaining time on a timer by 15 minutes.
15 Minute Speed Up is known to potentially be obtainable from opening Pile of Speedup, Bulk of Speedup and Mass of Speedup. The links for each item are below:
Note: This list may be incomplete.