Shortest path I found was something like: (.getEpochSecond (t/instant (t/zoned-date-time "1918-11-11T11:00:00Z[Europe/Paris]")))

Not much different but you can do

(-> (t/date "2020-01-01")
    t/midnight
    (t/in (t/zone "Europe/Paris"))
    t/instant
    .getEpochSecond)