What time zone are you in?

Steam is PST USA and usually does maintenance every Tuesday but it's possible to see this briefly at other time as well if they see issues that may need immediate attention.

What it could be also in during that time your ISP + Gateway is experiencing an IP# + Service refresh but that shouldn't result in 20 minutes of down time

most likely your isp resetting the modem/router on a daily schedule

cheap routers also do that since they dont have good enough firmware and enough ram to work 24-7 without crashing

also check steam stats to see busy times
https://psteamproxy.yuanyoumao.com/stats/content/

I get outtages a few in a while. But that's OK I get paid big coin 🪙 to be interrupted. Beta tester

Yes if you have certain Gateway, generally cheap one, it could simply be overheating and auto restarting when you happen to be online gaming at that same time all the time. A cheap one And the long downtime is due to the gateway/router reboot and auto refresh of service signal that could be occurring for you. You can easily monitor this with a simple app on your phone/tablet or via web browser and logged into your router.

I had that happen with a cheap one years ago from Comcast. But I talked them into giving me an expensive gateway meant for higher tier internet and once I got that box it never happened again.

You can check your gateway/router settings via web browser and make some changes. Such as instead of renew the IP once per week, set it to None or Forever.

You can also double check with your ISP as well to see if it's on their end.

this is not a steaming pile problem....this is your ISP as most force firmware updates at 12pm local time......i had this happen for 6 months in a row when i had SPECTRUM.....turned out they were trying to force a firmware update on my own modem that was not theirs.....

call tech support of your ISP at the time of it happening and see what they say......good luck....

at busy times, around 5-6p central steam will show as disconnected for a few minutes
logins and games will work, but sometimes store, downloads or forums will show errors

if it happens for longer than a minute, look at the modem and router lights to see if power is blinking
that often means it rebooted

If you are in a time zone where 12am for you is 4pm for Seattle Washington then yes tbat could be a Steam maintenance period however only on each Tuesday not every day.

So if you are GMT +0 London standard time, this would be 12am your time Wednesday and 4pm Tuesday for Valve in Seattle. This is generally when the update Tuesday occurs for Steam Community

But it should be more obvious it's a router and/or isp issue as it would kick you off your LAN/WIFI not just Steam when those are your culprits.

Or again like I said, the router settings.

Regardless of which gateway or router you have though it is a good rule of thumb to turn them off and power cycle them once a week. It flushes all the device and IP cache

I had that and it was the isp and router it would knock me off for two hours sometimes at random sometimes until 4am mainly it is the crap routers they supply.

Round up your gamer friends and compare notes. Check who has the same issues, what ISPs they are using, what model equipments they have and if it's always at the same time.

Also (just a blind guess) if you can try to not use the computer up till midnight and then use it for something casual (but checking if steam drops). The routers sometimes get backlogged on packages when there is too much traffic. You can (probably, but depends on the equipment you have) check that yourself. But if it's 2 people in different houses, then I doubt that. I don't think it's that, but could be that you have a more or less fixed "routine" and start gaming at more or less the same time. After xxxx hours or minutes the modem could be clogging up if it's really crappy, depending on usage.

I get it sometimes exactly at midnight GMT+1. Not an ISP issue as some are suggesting because everything works fine, only Steam disconnects. I figured it's just planned maintenance.

Thanks for the replies, guys. But I don't think this is a problem with my router etc. I'm from Switzerland and my buddy is from Germany. We're experiencing this outage at the same time. Steam is offline for both of us and it takes a moment for everything to come back (Steam comes back online, the friends list with voice chat takes the longest). Otherwise, the internet works continuously without any problems. If it's Steam updates that always come at exactly the same time, then support can tell me that. But not nonsense like I should update drivers, etc.