When Does "Alien: Advent" (2017) Take Place?
"Alien: Covenant - Advent" is a science fiction short film written by Will Melton that released August 15th, 2017. So when is "Advent" set?
It takes place on the fictional Alien vs. Predator timeline roughly in the year:
We know this because the first clear shot and the last clear shot both include the logo and name "WEYLAND-YUTANI CORP". The Weyland-Yutani Corporation is a company seen as two separate companies: the Weyland Corporation and the Yutani Corporation from "Alien vs. Predator" (2004), which takes place in 2004 AD, to "Prometheus" (2012), which takes place in 2093 AD. Therefore, it must be after their merger. In the expanded elements novel "Alien: Covenant - Origins" (2017), which takes place in 2103 AD, Indri Mithun says, ..."there are some among the Weyland contingent who still feel the need to assert themselves." and, soon after, "Most who survive such mergers quickly resign themselves to their new circumstances. But for a few, bad feelings can linger." This means the merger that creates the Weyland-Yutani Corporation hasn't happened yet in 2093 AD and is still recent in 2103 AD. So it is very likely after 2103 AD.

~2108 AD
We know this because the first clear shot and the last clear shot both include the logo and name "WEYLAND-YUTANI CORP". The Weyland-Yutani Corporation is a company seen as two separate companies: the Weyland Corporation and the Yutani Corporation from "Alien vs. Predator" (2004), which takes place in 2004 AD, to "Prometheus" (2012), which takes place in 2093 AD. Therefore, it must be after their merger. In the expanded elements novel "Alien: Covenant - Origins" (2017), which takes place in 2103 AD, Indri Mithun says, ..."there are some among the Weyland contingent who still feel the need to assert themselves." and, soon after, "Most who survive such mergers quickly resign themselves to their new circumstances. But for a few, bad feelings can linger." This means the merger that creates the Weyland-Yutani Corporation hasn't happened yet in 2093 AD and is still recent in 2103 AD. So it is very likely after 2103 AD.
Furthermore, it is probably before the Weyland-Yutani Corporation is dissolved. During "Alien Resurrection" (1997), which takes place in 2379 AD, Dr. Mason Wren says, "Weyland-Yutani, Ripley's former employer." ... "Oh, they went under decades ago, Gediman, way before your time. Bought out by Walmart. Fortunes of war." So it is probably before 2359 AD.
"decades ago" (plural) = at least 20 years
and
2379 - 20 = 2359.
More specifically, the short consists entirely of reports by the android David 8 on his activities from "Prometheus" (2012) to "Alien: Covenant" (2017), which takes place in 2104 AD. Between these two stories David was unable to transmit anything and it’s unlikely his extremely clinical mind would wait long to report his findings. However, in the final moment of the feature film "Alien: Covenant" (2017), which takes place in 2104 AD, he sends a recorded message under false pretenses that ends, "Hopefully, this transmission will reach the network and be relayed in 1.36 years." Though it was not made entirely clear, presumably that message at the end of the feature-length film as well as the longer one in this short are both transmitted to the same people (or ones in similar roles) at the Weyland-Yutani Corporation back on Planet Earth. Since the entirety of this short film is a new message and it begins, "I come to you with an olive branch.", presumably it is a reply message after the subterfuge with which he sent the first message has evaporated. If it takes "1.36 years" for one of these messages to reach Earth, it almost certainly takes another 1.36 years for one to travel back to David. And another 1.36 years– which is about 1 year and 4 months– for his reply to be seen back on Earth. Therefore, a reply message from David's location in outer space to Earth would be seen in three of these 1 year and 4 months cycles. It's most logical to place this found-footage short film when a viewer within the fictional universe (diegesis) of the film could first see it, in early 2108 AD at the earliest. If it isn't David's first reply, it must be later.
1 year and 4 months x 3 = 4 years
and
2,104 + 4 = 2,108.
It is the tenth chronological short film in the Alien vs. Predator timeline and it can be watched at its timeline point.

