Currently that is not possible to do that directly from JIRA UI. If you are using JIRA Standalone, there are plenty number of time tracking plugins available in Atlassian Marketplace, see this:
https://marketplace.atlassian.com/search/advanced?q=&application=jira&applicationVersion=&category=Worklog+%26+Time-tracking&pluginSystemVersion=&supportType=&license=&cost=&createdAfter=&createdBefore=&minDownloadsCount=&minimumStars=&search=true
However, if you are using Atlassian OnDemand, those plugins can't be installed per the Atlassian OnDemand Plugins Policy:
https://confluence.atlassian.com/display/AOD/Atlassian+OnDemand+Plugin+Policy
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