Two bugs in calendar display (the CLOCK ITSELF was already correct):
1. **Month enum had wrong order + non-retail names.** Old enum:
Snowreap=0, ColdMeet, Leafdawning, Seedsow, Rosetide, Solclaim, ...
At day-of-year 83 this gave month index 2 = Leafdawning. Retail's
@timestamp at the same moment shows "Seedsow 24". Fixed enum to
chronological order starting at year-anchor month Morningthaw, with
retail-canonical names:
Morningthaw=0, Solclaim, Seedsow, Leafdawning, Verdantine,
Thistledown, Harvestgain, Leafcull, Frostfell, Snowreap,
Coldeve, Wintersebb.
At day-of-year 83 → month 2 = Seedsow ✓
2. **ToCalendar returned relative year, not absolute Portal Year.**
We had AbsoluteYear() = relative_year + ZeroYear (=10) but
ToCalendar's Calendar.Year was the relative one. So acdream's
title bar showed "PY 106" while retail's @timestamp at the same
tick showed "PY 116". Fixed ToCalendar to add ZeroYear so the
exposed Calendar.Year matches retail's display.
3. **GameWindow title bar now shows the calendar.** Format mirrors
retail's @timestamp output:
"PY<Year> <Month> <Day> <Hour> (df=<dayFraction>)"
Lets the user read the same fields off both clients and confirm
clock parity directly. Drift > 1 hour = real bug.
Tests:
- Updated ToCalendar_PY10Day1_Morningthaw (renamed from PY0Day1_Snowreap)
- Updated ToCalendar_AdvancesCorrectly (Snowreap→Morningthaw etc.)
- Added regression: ToCalendar_TickAtSeedsow24Year106_MatchesRetailFormat
pinning a retail-known tick → retail-known calendar string.
The dayFraction formula (CalcDayBegin's `arg2 + zero_time_of_year`,
decomp 0x005a6400 line 434549) was already correct; an earlier-this-
session attempt to flip the sign was reverted in this same commit's
parent. The "few minutes drift" observed in dual-client comparisons
this session was a combination of:
- calendar label mismatch (this fix addresses)
- slot-boundary rounding (fixes itself)
- 1-minute wall-clock interpolation drift (within tolerance)
NOT a clock-formula bug. ISSUE #3 in docs/ISSUES.md is now misnamed
("Client clock drifts from retail"); plan to re-title or close in a
follow-up commit after the visual-divergence investigation lands.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Final piece of the retail-sync puzzle. Live Dereth dat has
GameTime.ZeroTimeOfYear = 3600 (verified 2026-04-23 diagnostic dump).
Our DerethDateTime hardcoded +7/16 × DayTicks = 3333.75, copied from
ACE's DerethDateTime.cs comment "tick 0 = Morntide-and-Half". The dat
is authoritative; ACE's comment is wrong by 266.25 ticks (~33 Dereth
minutes).
User-observed regression (2026-04-23):
acdream: middle-of-night (Darktide), clear, DayGroup "Sunny"
retail: near-pre-dawn (Foredawn), thunderstorm, stormy DayGroup
(both connected to the same ACE at PortalYearTicks=291134079)
Same server tick → different calendar extraction → the offset skewed
dayFraction AND pushed DayOfYear across a boundary at certain ticks,
feeding a different LCG seed into the DayGroup picker (FUN_00501990).
A single 266.25-tick offset error explains both the time mismatch and
the weather mismatch.
Code changes:
- DerethDateTime.OriginOffsetTicks — runtime-settable static, default
= DayFractionOriginOffsetTicks (3333.75, the legacy fallback).
Applied in DayFraction, Year, DayOfYear, ToCalendar.
- DerethDateTime.SetOriginOffsetFromDat(double) — called at Region
load.
- SkyDescLoader.DumpRegionSkyDesc dumps GameTime fields (and all 16
TimesOfDay entries) when ACDREAM_DUMP_SKY=1.
- GameWindow.LoadRegion adopts the dat's ZeroTimeOfYear after
LoadFromRegion, logs the before/after values.
Also dumps every Dereth TimeOfDay hour-boundary (0..15) so any future
calendar weirdness has authoritative ground truth in the log.
Build + 733 tests green (no test depended on the hardcoded offset).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Live verification (2026-04-23, Phase 3c launch): acdream picked
DayGroup[17] "Rainy" for PY106 day46 while retail at the same server
tick showed clear blue sky with white clouds (Sunny-ish). Root cause:
our port passed the RELATIVE year (106, i.e. years since tick-0) into
the LCG seed, while retail's TimeOfDay+0x64 is ABSOLUTE Year =
floor(...) + ZeroYear (baseYear=10 for Dereth GameTime). The offset
seeds the LCG with `seed = 106×7620+46` vs retail's `seed =
116×7620+46` — `10 × SecondsPerDay = 76200` apart, guaranteed to
land on a different DayGroup index.
Fix:
- DerethDateTime.ZeroYear constant (= 10) + AbsoluteYear(ticks) helper.
- GameWindow.RefreshSkyForCurrentDay feeds AbsoluteYear into the picker.
- LoadedSkyDesc.ActiveDayGroup(ticks) same.
- Calendar display and generic Year(ticks) stay relative; only the
LCG-seed path uses the offset. Matches retail FUN_005a7510:5300 which
explicitly adds baseYear to the relative year before stashing in
TimeOfDay+0x64.
Build + 717 tests green. Next visual check should show matching
weather with retail client side-by-side.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Decompile agent located the retail DayGroup selection function at
FUN_00501990 (chunk_00500000.c:1276). It is a straight-line 32-bit
signed LCG — NOT a ChanceOfOccur-weighted CDF. Replaces the SplitMix64
approximation from Phase 3a.
Algorithm (verbatim from the decompile):
seed = year * secondsPerDay + dayOfYear // TimeOfDay+0x64/+0x10/+0x68
hash = seed * 0x6A42FDB2 + 0x8ABE1652 // signed 32-bit LCG
index = floor(dayGroupCount * (uint)hash / 2^32)
if (index >= dayGroupCount) index = 0 // float-rounding safety
Uniform over all DayGroups. Dereth's 20 groups all carry ChanceOfOccur=5.0
so uniform matches the statistical intent; the weighted walk Phase 3a
attempted is NOT what retail does. The SecondsPerDay multiplier is
load-bearing — without it, adjacent years would share adjacent LCG
seeds and divergence from retail would recur annually.
Result (this session's local ACE):
server: PY106 ColdMeet 17 MorntideAndHalf, ticks=291130073
→ year=106, dayOfYear=(106×0 + 17 across ColdMeet) via DerethDateTime
→ retail picker returns a deterministic uniform index from LCG.
Acdream and retail now agree on the pick for any (Year, DayOfYear)
since both drive from the same server PortalYearTicks.
Changes:
- src/AcDream.Core/World/DerethDateTime.cs: add Year(ticks) and
DayOfYear(ticks) helpers (match retail TimeOfDay+0x64 / +0x68).
- src/AcDream.Core/World/SkyDescLoader.cs:
- SelectDayGroupIndex signature: (year, secondsPerDay, dayOfYear)
instead of the flat dayIndex used by the SplitMix64 approximation.
- Body: retail LCG line-by-line port with decompile citations.
- ACDREAM_DAY_GROUP env var still overrides (for A/B verification).
- src/AcDream.App/Rendering/GameWindow.cs: RefreshSkyForCurrentDay now
feeds Year / DayOfYear / SecondsPerDay=7620 to the picker instead
of a flat dayIndex. Composite `year*360+dayOfYear` still tracked
internally as the day-change key for provider-rebuild idempotence.
- docs/research/2026-04-23-daygroup-selection.md committed with the
full decompile trail (new agent-produced research).
Build + 717 tests green. User visual verification (retail side-by-side)
next.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
User observed: 'time is flipped — supposed to be day/evening, but shows
night/morning.' That's a ~half-day offset.
Root cause in ACE DerethDateTime.cs line 23:
private const double dayZeroTicks = 0; // Morningthaw 1, 10 P.Y. - Morntide-and-Half
ACE anchors tick 0 to Morntide-and-Half (slot 7 on the 0-indexed 16-slot
scale) — NOT Darktide (slot 0 = midnight) as our DayFraction function
assumed. Confirmed by DerethDateTime.cs:145:
private int hour = (int)Hours.Morntide_and_Half;
Fix: shift DayFraction by +7/16 * DayTicks (3333.75) so tick 0 maps to
its real calendar slot. Exposed as DayFractionOriginOffsetTicks constant
for documentation + downstream referencing.
Effect on sun: previously, server tick ~0 (just-booted ACE) produced
dayFraction 0 → midnight sky → night colors at noon real-time.
Now dayFraction 7/16 = 0.4375 → late morning sky → noon-ish colors
within 1/16 of a day, which matches what a user actually sees when
launching during daytime.
Tests updated for the corrected convention:
- DerethDateTime.DayFraction(0) = 7/16 (not 0).
- CurrentHour(0) = MorntideAndHalf (not Darktide).
- IsDaytime(0) = true.
- Midnight (Darktide, slot 0) is 9/16 of a day past tick 0.
- SkyState + WorldTimeDebug tests retargeted to the new frame.
Build green, 711 tests pass.
Ref: references/ACE/Source/ACE.Common/DerethDateTime.cs:23-25 + :145.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Client-side deterministic sky + weather + day/night system per R12.
Retail's model is 95% client-side: the server just delivers its
current PortalYearTicks (double, seconds since boot-seed) at login and
in TimeSync packets; the client computes everything else locally from
the constants in r12 §1.2 + ACE DerethDateTime.cs.
Core layer (AcDream.Core/World):
- DerethDateTime: retail-exact calendar (16 hours/day, 30 days/month,
12 months/year, 7620 ticks/day, 2,743,200 ticks/year). HourName enum
covers all 16 named half-hour slots (Darktide → GloamingAndHalf);
MonthName covers the 12 Derethian months (Snowreap → Frostfell).
DayFraction, CurrentHour, IsDaytime, ToCalendar.
- SkyKeyframe + SkyStateProvider: 4-keyframe default day/dawn/noon/dusk
with linear color + angular-wrap heading interpolation + slerp-like
shortest-arc lerp so heading wraps 350° → 10° don't tween backwards
through 180°. Default keyframe colors tuned to retail screenshots
(sunrise warm, noon white, sunset red, midnight deep blue).
- WorldTimeService: owns the live clock. SyncFromServer(ticks) sets
baseline; NowTicks advances by real-time elapsed. Exposes DayFraction,
CurrentSky, CurrentSunDirection, IsDaytime for the render thread.
This is the foundation Phase G.2 (dynamic lighting) consumes: lighting
uniforms are fed from CurrentSky's SunColor / AmbientColor / sun
direction, varying smoothly across the day.
Tests (16 new):
- DerethDateTime: midnight, half-day, wrap, Dawnsong, Midsong,
day/night flag at dawn vs Darktide-Half, year rollover, month
advance.
- SkyState: 4-default keyframes, noon-exact matches frame data,
midpoint lerps between neighbours, wrap across midnight doesn't
produce NaN, sun direction returns unit vector, WorldTimeService
sync + DayFraction at noon.
Build green, 587 tests pass (up from 570).
Ref: r12 §1 (Portal Year math), §2 (sky objects), §4 (color lerp).
Ref: ACE DerethDateTime.cs + NetworkSession TimeSync handler.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
