Today, on the 28^th of April, the FIA has released a new statement concerning the mandatory shutdown period all competitors have to observe. The initial 35 days span was not considered enough, accounting the present and future Coronavirus threat.
All the teams will have to keep their factories off for 63 consecutive days during the months of March, April, May and/or June.
Surrounded by uncertainty regarding future pandemic scenarios, the WMC informed that, 50 days after the start of the shutdown period, upon application by a competitor, and subject to the prior written approval of the FIA, each competitor may use the services of a maximum of ten personnel to work remotely on long lead time projects.

https://www.motorlat.com/notas/f1/15323/mclaren-challenges-ferrari-on-secret-engine-deal-your-ethics-prove-it

A shorter span of shutdown time has been imposed on the Power Unit manufacturers (Ferrari, Mercedes, Honda, and Renault): any work on the engine development has been forbidden for 49 consecutive days (including the original 35). Also for them, subject to the same rules and approvals as for all the competitors, ten people per constructor could work remotely after 36 days from the start of the period.

The Circus seems to be willing to hit the track in July, possibly with a season opener at the Red Bull Ring for the Austrian GP. In order to do so, it’s crucial for every team to keep every worker safe and those harsh -but fair- impositions from the FIA may be the best way to pursuit this goal.

https://www.motorlat.com/notas/f1/15321/is-f1-racing-at-silverstone-just-around-the-corner

We've set a target to begin the 2020 season on the weekend of July 3-5 at the Austrian Grand Prix

Here's more on our latest proposed plan for the season, once it's safe to start up again#F1 pic.twitter.com/17c1DuzsJf

— Formula 1 (@F1) April 27, 2020