Tiangong-1 is predicted to reenter in around April 1st, 2018 ± 4 Days*.
This prediction was performed by The Aerospace Corporation on 2018 March 20.
*Note: This prediction assumes an uncontrolled reentry (no thrusting).
The current estimated reentry window runs from the morning of 31 March to the early morning of 2 April (in UTC time); this is highly variable.
Update 11:00 CET, 31 March 2018
The space debris team at ESA have adapted their reentry forecast over the last 24 hr to take into consideration the conditions of low solar activity. New data received overnight gave further confirmation that the forecast window is moving to later on 1 April.
The team now are forecasting a window centred around 23:25 UTC on 1 April (01:25 CEST 2 April), and running from the afternoon of 1 April to the early morning on 2 April. This remains highly variable.