A Leave Year is the period of time that your Leave spans, this is a 12 month period and can start at any time in the year. Generally, Leave Years run from January to December, but yours may start at a different time, depending on policy.
You may be required to change this at some point, e.g. from January to December to run from May to April. Leave Years are attached to Leave Profiles, so all users within a Leave Profile will have the same Leave Start Month. It's possible to change this for the entire organisation or certain Leave Profiles.
If you want to change this for specific Leave Profiles, go to System Config > General Settings > Leave.
Untick the box 'Enforce consistent Leave Start Month' then click Save.
Then, go to Leave Admin > Leave Profiles, select the Leave Profile you want to edit and in the Main Details tab you will be able to select a new Leave Start Month.
Once you save this, a dialog will pop up with a warning. You'll need to go to the Adjust Allowance Range tool to ensure your employees' allowances are updated correctly following the change. Click OK and you'll be taken to the Adjust Allowance Range tool.
For each Team and Leave Profile, you will be able to see a view of the previous year's balance and the new year's balance. Check these are correct and then click Save Changes.
For more information on the Adjust Allowance Range tool, take a look at the article here.