Time Development Points
Time Development Points (TDPs) are used to increase attributes, as well as for buying new spell slots and forgetting learned spells. (See: Spell Library)
In order to use TDP's to raise a stat, one must go to a designated room for training that particular stat and type TRAIN, then STUDY to confirm. Training rooms for each stat are available within or near every major city.
A new character is given 600 TDPs right out of the Character Manager. After that, the only way to gain more TDPs is by circling or obtaining new ranks in skills.
TDPs from Circling
Each time you circle, you will gain a base amount of TDPs plus a bonus based on your circle. Below circle 10 you will always get a base of 50 TDPs. Between circles 10 to 20 you will get either 50 or 100 base TDPs. (We do not know what triggers the jump from 50+ per circle to 100+ per circle, but it definitely does not involve stat average.) After circle 20, you will always gain 100 TDPs as a base. The bonus TDPs are always equal to the circle you just attained. For example: if you attain circle 27, you will get 127 TDPs.
Actually, it is based on stat average rounded down. In order to obtain 100 tdp base you must have your stats total divided by 8 rounded down to the nearest whole number, you must circle past this #. IE. at 87 total stats added you would need to hit 11th for 100. At 88 you would now need to hit 12th, thus making it effective to hold off spending tdps. I've tested this on about 5 characters now and it seems to hold true.
TDPs from Leveling Skills
Each time you gain a new rank in any skill, the integer value of that rank is added into a hidden pool (the TDP pool). If at any time the total in the pool reaches or exceeds 200, you gain one TDP and 200 is subtracted from the pool. This also applies for multiples of 200: if the TDP pool reaches 400, you gain two TDP's and 400 points are subtracted; for 600 you get three TDP's and 600 is deducted from the pool, etc.
For example, let's assume that your TDP pool is currently zero. You increase your Perception skill to attain rank 150. 150 points are added to the TDP pool. You then increase your Leather Armor skill to rank 66. 66 points are added to the TDP pool, making a total of 216. You gain one TDP, and 200 points are subtracted from the TDP pool leaving 16 points. Next, you increase your Magical Devices skill to 197. Your pool increases to 213, you gain yet another TDP, and the pool is reduced to 13.
Since the experience change where all tertiary skills less than 100 ranks are learned at the rate of secondary skills, it is considerably easier than it was to level tertiary skills for the sake of TDPs alone. Leveling a single skill to 100 ranks will result in a gain of 25 TDPs when all is said and done. Leveling a skill to only 50 will result in a gain of 6 TDPs.
To determine how many total TDPs you will receive for leveling a skill from zero to n, where n is the target rank of the skill, use this formula:
Death and Losing TDPs
When you lose ranks from memory decay as a result of death without rejuvenation, your TDP pool will be reduced by the ranks you lost. If this sends the TDP pool below zero you will lose a TDP, and 200 will be added to the pool. This process makes it possible to have a negative number of TDP's.