  Bars strongly influence the distribution of gas and stars within the central
regions of their host galaxies. This is particularly pronounced in the star
formation desert (SFD) which is defined as two symmetrical regions either side
of the bar that show a deficit in young stars. Previous studies proposed that,
if star formation is truncated because of the influence of the bar, then the
age distribution of stars within the SFD could be used to determine the epoch
of bar formation. To test this, we study the properties of SFDs in 6 galaxies
from zoom-in cosmological re-simulations. Age maps reveal old regions on both
sides of the bars, with a lack of stars younger than 10 Myr, confirming the SFD
phenomenon. Local star formation is truncated in the SFDs because after the bar
forms, gas in these regions is removed on 1 Gyr timescales. However, the
overall age distribution of stars in the SFD does not show a sharp truncation
after bar formation but rather a gradual downturn in comparison to that of the
bar. This more subtle signature may still give information on bar formation
epochs in observed galaxies, but the interpretation will be more difficult than
originally hoped. The gradual drop in the SFD age distribution, instead of a
truncation, is due to radial migration of stars born in the disk. The SFD is
thus one of the only regions where an uncontaminated sample of stars only
affected by radial migration can be studied.
