12 and 24 hour search lookbacks not converted to start timestamp correctly

[tiffon]

Description

A JS bug causes start timestamp for the 12 hour and 24 hour lookback to be the same as the end timestamp.

Steps to reproduce the issue:

1. Set the search lookback to either 12 hour or 24 hour
2. Execute a search

Describe the results you received:

The start and end timestamps GET query parameters are the same.

Describe the results you expected:

The start timestamp should be the adjusted based on the lookback.