You can use different calendars based on custom field value by simply defining multiple SLAs with different calendars and then using JQL option to target different field values. Here are the detailed steps:

1. Create an SLA for each calendar that you would like to use.
2. Configure these SLAs based on your requirements.
3. For each SLA, add an additional JQL clause to target the desired custom field values.

As you might have noticed, you are not limited when it comes to custom field values for this trick. You can use anything possible in JQL to apply different calendars such as assignee, issue type creation date, etc.

Example

Requirements

There are multiple support teams dealing with support requests for two projects.
India and US team are major teams.
The same SLA times apply to these teams but they operate in very different time zones and this makes it hard to track SLAs with a single calendar.
We would like to apply time zone specific calendars for US and India teams and 7x24 calendar for all other teams.

Scope: Only for projects FastDev Support and SecureBits Support
Start: Open status
End: Resolved status
SLA Duration: 10d
Calendar:

• If team is selected as "India Team" on the issue then "India calendar" should be used
• If team is selected as "US Team" on the issue then "US calendar" should be used
• If team is not "India Team" or "US Team" then 7x24 calendar should be used

Solution

Define 3 SLAs as follows

Notice how we targeted those 3 SLAs for different teams using an additional JQL clause.