The epoch of bar formation in the Milky Way

A key event in the life of the Milky Way is the formation of the bar. The Milky Way bar has restructured the disc, been slowed by the dark matter halo and funnelled gas towards the Galactic Centre. It is then important to know the period of time over which these processes have been effective. Although the bar is formed from stars that are older than the dynamical age of the bar, the nuclear stellar disc (NSD) formation was likely coincident with bar formation. The NSD region is highly crowded and obscured, but Mira variables make bright age tracers of this region. I will describe work on discovering Mira variables in this region of the Galaxy using the VVV survey, the calibration of the Mira variable period-age relation using nearby counterparts observed by Gaia and the dynamical modelling of the NSD Mira variable proper motion distribution. The dynamical modelling reveals the NSD likely formed around ~7-8 Gyr ago. I discuss how this event fits into the timeline of events in the early Milky Way.