Time periods

Firefly III shows you your finances per month. In your settings you can change this. For example, you can choose to show your finances yearly, weekly or in a "month to date"-style. More options exist of course, just check out your settings.

Custom daily cycles

Firefly III does not (and will not) support custom cycles. For example, you will not be able to make Firefly III go from the 24th of one month to the 23rd of the next month. This is requested a lot, because it matches their salary payment cycles. Likewise, it is not (and will not) be possible to have a 2-week, 4-week cycle, or a 13-week cycle.

In personal finances, I believe it is not a good idea to have your paycheck determine your schedule and thus, your life. If you are serious about saving money, you will want to have a fixed schedule that does not change. This way, you can plan ahead and make better decisions. I am opinionated on this topic, so Firefly III is as well.

Using a schedule (a monthly schedule is my favorite) you can track expenses and income in a reasonably long period, you can compare both months and seasons, and as a bonus the month itself will tell you how far along you are in your current cycle.

To learn more about this, see also the page on personal finances.