Oh, those were the days when the developer released a Christmas update in December...
v0.20.16: 31 Oct 2022 (Small Secret Pre-tech part 6) -> 1 month
v0.20.15: 25 Sep 2022 (Pre-tech part 5) -> 5 months
v0.20.14: 29 Apr 2022 (Pre-tech part 4) -> 2.5 months
v0.20.13: 19 Feb 2022 (Pre-tech part 3) -> 4 months
v0.20.12: 22 Oct 2021 (Pre-tech part 2) -> 3 months
v0.20.11: 01 Jul 2021 (Pre-tech part 1) -> 3 months
v0.20.9: 31 Mar 2021 (Main Story grand finale) -> 5 months
v0.20.7: 25 Oct 2020 (Odette Halloween) -> 1.5 months
v0.20.5: 08 Sep 2020 (Main Story 2) -> 4 months
v0.20.1: 05 May 2020 (Main Story 1) -> 5+ months
v0.19.5: 20 Dec 2019 (Consuela) -> 2 months
v0.19.1: 19 Oct 2019 (Eve) -> 4.5 months
v0.18.6: 05 Jun 2019 (Jenny) -> 1 month
v0.18.2: 04 May 2019 (Jenny) -> 4.5 months
v0.17.5: 16 Dec 2018 (Daisy) -> 1- month
v0.17.1: 29 Nov 2018 (Diane) -> 4 months
v0.16.1: 31 Jul 2018 (Roxxy) -> 3+ months
v0.15.3: 17 Apr 2018 (Teachers) -> 4 months
v0.14.5: 20 Dec 2017 (Debbie) -> 1.5 months
v0.14.3: 01 Nov 2017 (Aqua) -> 0.5 months
v0.14.1: 13 Oct 2017 (Mia) -> 2- months
v0.13.1: 22 Aug 2017 (Tammy, June) -> 2 months
v0.12.7: 26 Jun 2017 (Debbie, Jenny, Diane) -> 1 month
v0.12.1: 22 May 2017 (Debbie, Jenny, Diane) -> 2.5 months
v0.11.0: 03 Mar 2017 (Debbie) -> 2.5 months
v0.10.0: 23 Jan 2017 (Diane)
What xmas update though ? We got 3 updates in December, most of which weren't for xmas content. We actually got more Halloween-themed updates