Hi,
Jira should show the time by the time zone set in the user profile. All time fields users see in Jira should be converted from the server time zone to the timezone set for the user. This community post explains different aspects of the time zone settings: Issues with different update date.
You should change the Time zone setting in the eazyBI data import options to the same you set in your Jira user profile settings. The time should be imported into eazyBI the same way as you see it in Jira.
You should not need to use Javascript for such time zone conversion.
Kindly,
Janis, eazyBI support