The issue:
Cooldown time drifts because it is based on the exact time you cast it, which is always later than the previous.
An explanation:
An alchemist wants to use a transmutation which has a 24hr cooldown.
They do so at 18:00, so the next available opportunity to perform this action is after 18:00 the following day.
Even if they initiate the transmutation immediately after the cooldown ends on the following day, the time at which they are next able to use the transmutation will drift later into the day. The next time becomes 18:01, then 18:35, and further to 21:00.
The minimum amount of drifts is equal to the cast time of the spell, but more likely the player will only realize it is available several minutes or even an hour later. This quickly cause the cooldown to end during hours the player would have logged off, such as for work or sleep. Minutes and Hours become entire cooldowns worth of time lost. It is a mechanic which feels like it is not conscientious to the player's availability, and unfairly punishes the player with missed opportunity that their chosen profession offers.
A Solution:
Make the cooldown for the ability reset upon the server's ingame day beginning at 00:00. This does not alter the rate at which the player is able to use the ability, however it offers a natural forgiveness to what time of day you use the ability on. They only need to use it whenever it is available, and not have to worry about any lost time.