Skill training
This needs an overhaul to be used in games.
I find the DnD system overly rigid with skills, so I looked at some homebrew rules to train skills outside of actual leveling and tried to come up with a good system. One of the ones I looked at used experience to get skills, but rather than that, I'm playing with *time*.
Please note, that the system already assumes that the characters are practicing the skills they would like to improve in as they adventure. This system requires 8 hours a day of studies, 8 hours of recreation and 8 hours of rest 7 days a week. It's fulltime training in whatever skill it is, and is very demanding. The DM may accept some nottoo demanding activities in the recreational time a few times per week (such as a social engagement), or a few hours per day (such as an apprentice job). It also requires either excellent source material (such as books in a library) or an instructor to train. There is frequently a gold cost involved as well as the time spent.
DMs will need to decide how they want to handle partial days of training. Generally there is no rounding in the calculations.
Contents
Trained vs 'natural' skill
Trained skill ranks are simply added on top of regular skills and a character can not train more than her maximum number of ranks in a skill. The main difference is that the time it takes to train is in relation to how many ranks have been trained before, rather than total skill ranks, so the player needs to keep track of how many skill ranks she has trained out of her total for the given skills.
Training Efficiency Value
Depending on how smart the character is, the character learns at a certain speed and can go longer without starting to forget their training. This is calculated in the TEV:
 Add up the following modifiers:
 Each point of Intelligence bonus, times 0.5
 Class has 2 skillranks/lvl = 0
 Class has 4 skillranks/lvl = 0.25
 Class has 6 skillranks/lvl = 0.50
 Class has 8 skillranks/lvl = 0.75
 The sum is your Traning Efficiency Value (TEV).
Training time
Quite simply, the time it takes to gain one skill rank is 2 weeks plus one for each rank already trained previously. So, for number of trained ranks:
 Gain +1 rank = train for 2 weeks. Total time: 2 weeks for 1 rank.
 Gain +1 rank = train for 3 weeks. Total time: 5 weeks for 2 ranks.
 Gain +1 rank = train for 4 weeks. Total time: 9 weeks for 3 ranks.
 Gain +1 rank = train for 5 weeks. Total time: 14 weeks for 4 ranks.
 Gain +1 rank = train for 6 weeks. Total time: 20 weeks for 5 ranks.
 Gain +1 rank = train for 7 weeks. Total time: 27 weeks for 6 ranks.
 Gain +1 rank = train for 8 weeks. Total time: 35 weeks for 7 ranks.
 ...
Then make final modifications:
 If it's a crossclass skill, multiply result by 1.5.
 Multiply TEV with the amount of weeks of training and subtract this amount of days from the training time.
 This is the total training time.
Example: Lys the fighter (int 10) has 6 skill ranks in Diplomacy and is talking with a professor of rethoric to improve her skills in Diplomacy during downtime from adventuring. She has already had a little bit of help from the professor before, and gained 1 skill rank. The next rank she gains is the second trained rank, and so 1 previous rank is calculated rather than 6 when determining how long it will take to train, which means it will take a total of 3 weeks and when she is finished she has spent a total of 5 weeks together with the professor.
Pause in training
If the character does not have access to sufficient training for a period of time before acquiring a skill rank, she starts to forget what she learned. The amount of days that she can go without forgetting is: Total skill ranks + TEV (minimum 3 days).
Any additional pause after that will decrease the effective count of training days by one for each additional day without effective training.
Multiclassing Midtraining
A character that is training a particular skill and changes classes before finishing her training (getting a new TEV) can choose between keeping her current progression or recalculating it.
If she chooses to recalculate:
 Subtract the days trained from the training time (in days) to get remaining days.
 If it's a crossclass skill, multiply result by 1.5.
 Multiply TEV with the amount of remaining weeks and subtract this amount of days from the remaining days.
 This is the new remaining days to train.
Example: Hannah is a lvl 3 Fighter with an Intelligence score of 15 (TEV = 1.0). She is one week into training her third skill of Handle Animal. She is now acquiring a level of Rogue and has picked Intelligence as her ability increase, getting a new TEV of 2.25.
The training time is 4 weeks, of which she has done one already. Her Rogue TEV with ability increase is 2.25 (0.5*3+0.75), shortening remaining days needed to 14 and one quarter days (213*2.25) which is just over 2 weeks left to train.
Notes
Note 1: To be entirely in line with the rest of the rules, the difference should be greater between skill monkeys and other classes, but then it's TOO easy to max out everything. This is mainly meant for players to get a few skill ranks in a few skills they may not otherwise invest in.
Note 2: The ability modifier is here more important than skillmonkey class, if you count a score of 18 as "normal". However, in most games having scores of 16 is pretty good, and I think that should be comparable to class ability, and it would also reward nonskillmonkey classes with high intelligence.
Aand some classes are simply a little slow on the uptake! :)
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