[thomasklemm]

This fixes Time.now in lobsters at 2026-07-01 12:00 UTC, during boot and in the benchmark block, to keep its work per iteration from depending on the date it runs. #572 is an alternative that fixes the clock at a different instant; merge one of the two.

On main, in lobsters' US Central time zone, when a lookback such as 70.days.ago crosses a DST change, ActiveSupport looks up the zone period again: 1,476 extra lookups per pass on 2026-11-05, none in July. On Dec 25 and Jun 28 the logo changes too. With the clock fixed, the tzinfo lookup counts were the same on every tested date.

Across the four tested dates, allocations per iteration varied by 0.01%, against 1.37% on main (Ruby 4.0.9, system clock set to each date):

	2026-11-05	2026-12-25	2027-03-20	2027-06-28	spread
main	657,758	657,025	657,811	648,912	1.37%
this PR	648,889	648,916	648,913	648,872	0.01%

Response bodies are byte-identical between runs on 2026-11-05 and 2027-01-20, apart from CSRF tokens. The harness keeps the real clock. Date.today, DateTime.now, Time.new without arguments and SQLite's 'now' stay live. Cache entries and the session no longer age. TRACK_AR_TIME uses the monotonic clock.

For lobsters' history this is a one-time step of up to −1.35% objects against runs whose lookbacks cross a DST change (roughly November to January and mid-March to mid-June).

How this was measured

Objects: GC.stat(:total_allocated_objects) around each iteration of the default harness, WARMUP_ITRS=1 MIN_BENCH_ITRS=3, mean of the 3 measured iterations per date, spread = (max − min) / min of the per-date means, system clock set with libfaketime (FAKETIME='@<date> 12:00:00' FAKETIME_DONT_FAKE_MONOTONIC=1), cg_harness.rb with CG_DUMP=0. Responses: raw_dump.rb writes status, headers and body of all 114 requests in the pass after one warmup pass; raw_cmp.rb blanks the authenticity_token values, the csrf-token meta tag and the random headers (session cookie, ETag, X-Request-Id, X-Runtime) and compares the rest byte for byte: 0 of 114 differ. Lookups: dst_probe.rb.