its better to use `date + Time.zone.utc_offset` rather than `Time.zone.parse(date.to_s)` if you are worried about performance, and if you only need the value, not the whole object.

parse_time_zone.rb

require 'benchmark/ips'
require 'active_support/all'


LOOP_FOR = 100_000
Time.zone = 'Hawaii'
DATE = Time.current.getutc

# a certain custom time format
Time::DATE_FORMATS[:local_db] =
  ->(time) { time.strftime(Time::DATE_FORMATS[:db]) }

def faster
  offset = Time.zone.utc_offset
  LOOP_FOR.times do
    (DATE + offset).to_s(:local_db)
  end
end

def fast
  LOOP_FOR.times do
    DATE.in_time_zone.to_s(:local_db)
  end
end

def slow
  LOOP_FOR.times do
    Time.zone.parse(DATE.to_s).to_s(:local_db)
  end
end

Benchmark.ips do |x|
  x.report('use and cache offset')      { faster }
  x.report('use zone')                  { fast }
  x.report('parse with zone')           { slow }
  x.compare!
end

result.txt

Warming up --------------------------------------
use and cache offset     1.000  i/100ms
            use zone     1.000  i/100ms
     parse with zone     1.000  i/100ms
Calculating -------------------------------------
use and cache offset      3.053  (± 0.0%) i/s -     16.000  in   5.288739s
            use zone      0.588  (± 0.0%) i/s -      3.000  in   5.280270s
     parse with zone      0.151  (± 0.0%) i/s -      1.000  in   6.605711s

Comparison:
use and cache offset:        3.1 i/s
            use zone:        0.6 i/s - 5.19x  slower
     parse with zone:        0.2 i/s - 20.17x  slower