A user on reddit did some calculations claiming it was accurate. The user estimated it to be around 5 days based on growth rate of ice, the air speed of an
unladen swallow raven, and approximation for distances and dragon speed.
Link to the original post
I've broken down their answer but provided a link to the original just above.
- Gendry's run, around 4 hours:
- The Seven (/Twelve with the additional rangers) likely weren't travelling in a line straight north. They were searching for the Army of the dead, and specifically a lone wight or, as they ended up finding, a small party of wights. This means they would likely be travelling in a zig-zag type of walk to cover as much area as possible. Furthermore sticking to higher altitude so they would have that over their opponents (As they end up looking down at the wights in the canyon).
- Gendry running at full speed would require about 4 hours to cover a significant amount of ground. We can't be sure how many days the Seven had been travelling for, but if we assume it to be about 2 days of zigzagging over quite a large area it would be a reasonable assumption for it to take Gendry about 4 hours to run back.
- The Raven likely took around 3 days to get from Eastwatch to Dragonstone.
- A raven flying from Eastwatch to Winterfell would be about a day:
Homing pigeons have been recorded to be able to reach speeds of up to 50mph and although discussions have taken place to the speed of ravens, although no real speed is given, we are led to believe that in-universe ravens are quicker and stronger that in-universe pigeons as stated by Maester Aemon:
Doves and pigeons can also be trained to carry messages,” the maester [Aemon] went on, “though the raven is a stronger flyer, larger, bolder, far more clever, better able to defend itself against hawks ...
- Continuing this idea to flying to Dragonstone. It's about the same distance from Winterfell to Kings Landing as it is to Dragonstone. The show claims it to be about 1000 miles from Winterfell to King's Landing (according to the user). This gives us about 3 days of raven flight if we take the 500 mile per day cap set by the users in the discussion above.
- Dany and her dragons likely took around 8 or so hours to fly to "Snow team 6"
- The user approximated around 125mph for a Dragon with a rider. Given the size of the Dragons, this seem possible as a normal hawk is able to fly around 70mph. Whether wingspan changes speed is unclear but big birds tend to be quicker than small birds.
This gives us about 5 days of total travel from Gendry running to the Dragons arriving.
The ice aspect is a bit strange. As 10˚F is around -12˚C and doesn't seem that cold for Gendry to be crying about the freezing cold weather. It was likely closer to -30˚C to -40˚C which I guess would make the ice freeze twice as quick. But bearing in mind that the Ice was thin in the first place there might be something that was preventing the water from garnering thickness very quickly. Such as the hot springs which exist naturally in the north (Winterfell's walls, Ygritte and Jon's cave) may have slowed the freezing of the water.
There are theories it can be done in ~3 days.
If we take the 500 miles per day, and the fact that white Ravens can fly from Old Town to Winterfell, it's possible a Raven can fly to Dragonstone from Eastwatch directly. This would cut down travel time to about 2 days of raven flight (at 50mph with rest). If we take a Dragons airspeed to be around 200mph it would do the return flight in 5 hours. Easily done in ~three days, allowing for better calculation for the rate of freezing of the water.