Five challenges in five topics that can be easily achieved in a day with little to no planning. A daily challenge is a small test to an idea, topic or area. The goal is to expand and explore, but requiring as little of a time commitment as required to try it out.
Five challenges in the same five topics but may involve a little bit of planning and maybe another participant. A weekly challenge is a little more focused and the start to getting more serious in terms of effort and time commitment. They shouldn't be too hard to complete, but also not something that can be completed without trying.
Five challenges, likely not possible to do on day to day basis without significant effort. Something to plan, and is the real meat of taking on a challenge. Not to disregard the shorter time frames, but at this point it you are just starting to try something more seriously and have taken on "the challenge". It should take multiple days and should not be easy. If it is too easy, and it's a new experience... Maybe its a talent or natural skill? The work involved was too enjoyable? Should I give you something more worthy of your efforts?
No longer a short list of challenges to undertake. Choose a long term challenge and check back here to evaluate. At this point, the list is not finished as I'm still deciding how this and the next section should be handled.
Entirely personal and something to remember the year by. May change if it makes sense to do so.