⭐ Merited by bitmover (1)
You'll be pleased to know that ProtonDrive is underdevelopment, as also confirmed by their twitter account here: https://twitter.com/protonmail/status/988808782951133184.
And the Calendar is also very near. 
They said it would be released this summer, which means that it's close (even if already late).
Quote
Proton Calendar will be released in beta near the end of this summer along with the redesigned ProtonMail 4.0 which is coming soon also.
https://twitter.com/ProtonMail/status/1148348751486115840And
Quote from: ProtonMail
Our calendar is under active development right now. It is very challenging to build in a completely encrypted way, that is why it is taking longer. We will have more to share about this later this summer. Thank you for your patience.
https://www.reddit.com/r/ProtonMail/comments/bwqshx/proton_calendar/eq2juat/As far as I remember(read it on Reddit) the new release date target of the beta is at the end of the year(hopefully the final date). If I remember correctly, their first target was last year. I'm not saying that they're going to delay this again, but yea just fyi. I became really impatient due to the delays so I just looked for an alternative instead.