[Openresty] %z だと nginx の iso_8601 の format と異なるので(: がない)、format を揃える

result.md

FYI: https://qiita.com/sfujiwara/items/b227b3ca6a1e8f104bc9

$ date +%z
+0900

$ /path/to/resty start_time.lua
1970-01-01T09:00:00+09:00

start_time.lua

now   = os.time()
offset = os.difftime(os.time(os.date("*t", now)), os.time(os.date("!*t", now)))
hour = math.floor(offset / 3600)
min  = (offset / 60) % 60

timezone = nil
if offset < 0 then
  timezone = string.format("-%02d:%02d", hour, min)
else
  timezone = string.format("+%02d:%02d", hour, min)
end
ngx.say(os.date("%Y-%m-%dT%T", ngx.req.start_time()) .. timezone)