JIRA converted Time Tracking field which is Original Estimate to hours even though the Format used is Day. So far, this is tested against JIRA 4.1.2, JIRA 4.2.1

To replicate this problem with Hours Per Day=8:

1. Enable Time Tracking and set the Hours Per Day equal to 8
2. Choose Day Format
3. Create a ticket and set the Original Estimate to 0.1d. The value will remain as 0.1d.
4. Create a ticket and set the Original Estimate to 0.125d. The value will be converted to 1h
5. Create a ticket and set the Original Estimate to 0.25d. The value will remain as 0.25d

To replicate this problem with Hours Per Day=24:

1. Enable Time Tracking and set the Hours Per Day equal to 24
2. Choose Day Format
3. Create a ticket and set the Original Estimate to 0.1d. The value will remain as 0.1d.
4. Create a ticket and set the Original Estimate to 0.125d. The value will be converted to 3h
5. Create a ticket and set the Original Estimate to 0.25d. The value will remain as 0.25d

To replicate this problem with Hours Per Day=6:

1. Enable Time Tracking and set the Hours Per Day equal to 6
2. Choose Day Format
3. Create a ticket and set the Original Estimate to 0.1d. The value will remain as 0.1d.
4. Create a ticket and set the Original Estimate to 0.125d. The value will be converted to 0.75h
5. Create a ticket and set the Original Estimate to 0.25d. The value will remain as 0.25d

On related note, JIRA will throw the following System Error if the Hours Per Day is 7.5 and the value is set to "0.125d":

java.lang.IllegalArgumentException: Error occurred while converting time estimates:Specified decimal fraction duration cannot maintain precision