CycleMinutes is the full day, sunrise to sunrise (vanilla 30; 0.5 to 1440). DaytimeMinutes is sunrise to sunset — the stretch the game counts as day, when the Day N banner fires and, halfway through, sleeping opens (vanilla 21). NightMinutes is sunset to sunrise, through dusk, the midnight day-counter tick and dawn (vanilla 9). Both from 0.25 to 1440.

LengthRule decides which gives way when daytime + night is not the cycle. Agreeing values give the same answer under every rule.

FitToCycle keeps the cycle exact and scales the other two, keeping their ratio. A rule that would leave a segment under 15 seconds floors it there and stretches the cycle instead, and the log warns.

The sun's pace depends on the two lengths alone: 180 / DaytimeMinutes degrees a real minute by day (vanilla 8.57) and 180 / NightMinutes by night (vanilla 20). The vanilla night is faster than the vanilla day and stays so at any setting that keeps the 70/30 split; a 45/15 split makes it 12 against 4.

Sleeping still opens in the afternoon — the middle of daytime — and through the night, and still skips to the next sunrise in 12 real seconds whatever the lengths, now aimed at your sunrise, so a pre-dawn sleep never skips an extra day or rewinds the clock.

ProductionScale is a multiple of vanilla: 1 vanilla, 2 twice as fast, 0.5 half (0.01 to 100). ProductionBasis says what 1 means:

• RealTime (default) — vanilla production per real minute, whatever the cycle length. A crop that took 30 real minutes in vanilla still takes 30 real minutes; on a 60-minute day that is half a day. The game day is stretched to fit.
• GameDays — vanilla production per game day, the economy of the older server-only line. The day stays 1800 game-seconds and the clock slows or speeds to fit, so on a 45-minute day a crop still takes one day, which is now 45 real minutes.

Raids, events, Rested, food and comfort run on real time, so a longer day gets more raids per game day and a shorter one fewer.

On every machine, from the same synced settings and the same solver:

• EnvMan.m_dayLengthSec is set to L when the world loads and whenever the settings change.
• EnvMan.RescaleDayFraction is replaced by the same function with s and e for its knees.
• EnvMan.GetMorningStartSec returns day x L + L x s, and EnvMan.SkipToMorning uses s where vanilla hard-codes 0.15. The night is still skipped in 12 real seconds.
• ZNet.UpdateNetTime adds dt x R to the world clock instead of dt — on the server while anyone is connected, and on each client between the server's pushes.
• ZNet.GetWrappedDayTimeSeconds, which only the water and the fish read, returns the clock divided by R while WaveSpeed = Vanilla.

The sea. Water time is the game clock, so at ProductionScale = 3 the waves would roll three times as fast, and a storm would move the surface under a hull fast enough for the game to count it as a slam. WaveSpeed = Vanilla feeds the water real time instead, identical on every machine. While the clock runs at vanilla rate the two are the same; changing the rate with Vanilla selected moves the wave pattern once, on every machine at the same moment.

When the day length changes on a running world. The day number is clock / L and the time of day is clock mod L, and the clock is never re-based — doing that would make every timestamp in the world jump by hours. So the first time a world runs with a different L, both shift once: a world on day 277 of 1800-second days reads day 138 at L = 3600. After that everything is consistent again, and the log prints exactly what happened. L changes when CycleMinutes or ProductionScale change under RealTime, or ProductionScale under GameDays; changing only DaytimeMinutes or NightMinutes moves where the sun is right now, not the day number.

New worlds start with the clock at 2040 game-seconds: on an 1800-second day that is day 1, just before sunrise; on a 3600-second day, day 0, just past noon. Cosmetic.

Raw day-fraction is (clock mod L) / L; RescaleDayFraction maps the stretch from s to e onto the visual 0.25..0.75 in which the sun is up and EnvMan.IsDay is true. So daylight lasts (e - s) x L / R real seconds and a whole day L / R.

Given T (cycle), D (daytime), N (night) in real minutes and the production scale P:

1. Reconcile the lengths so that D + N = T, by LengthRule (table in chapter I).
2. Daylight share f = D / T. Vanilla 0.7.
3. Requested clock rate: RealTime: R0 = P · GameDays: R0 = P x 1800 / (60 x T).
4. Day length L = round(R0 x 60 x T) game-seconds — a whole number, because the game stores it as one.
5. Exact clock rate R = L / (60 x T), recomputed from the rounded L so a day takes exactly T real minutes; the rounding lands on R, by at most 0.5 / L relative, and the log prints the production scale actually realised.
6. Sunrise and sunset s = 0.5 - f / 2, e = 0.5 + f / 2. Noon stays at raw 0.5 and midnight at raw 0, as in vanilla.

What follows, on every machine:

daylight            =  f x L / R          real seconds  =  60 x D       (exactly D minutes)
night               =  (1 - f) x L / R    real seconds  =  60 x N
full day            =  L / R              real seconds  =  60 x T
production          =  R                  x vanilla, per real minute
                    =  L / 1800           x vanilla, per game day
a vanilla day of work (1800 game-seconds of growth, smelting, fuel)
                    =  30 / R             real minutes  =  1800 / L game days
sun, by day         =  180 / D            degrees per real minute   (vanilla 8.57)
sun, by night       =  180 / N            degrees per real minute   (vanilla 20)

P changes R and L together and in the same ratio — which is why production is a dial of its own: the sky looks identical at ProductionScale = 1 and = 3; only the crops, the smelters and the weather know the difference.

The last row is step 5 at work: 1.37 x 60 x 33.3 = 2737.26 rounds to 2737, the cycle stays exactly 33.3 minutes, and the realised production scale is 1.36987.

Vanilla is a fixed point. At the defaults the solver returns L = 1800, R = 1, s = 0.15, e = 0.85, and the patched RescaleDayFraction is bit-for-bit the vanilla function. The mod then changes nothing at all — checked by its own test suite and by the self-check in the log.

BepInEx/LogOutput.log — on the server at startup and after every edit, on each player's game as the values arrive (their lines say client instead of dedicated server). A 60 / 45 / 15 server:

[Message:DvergrAstrolabe] cycle (startup, no world loaded):
  settings   : CycleMinutes = 60, DaytimeMinutes = 45, NightMinutes = 15, LengthRule = FitToCycle, ProductionScale = 1, ProductionBasis = RealTime
  1 lengths  : FitToCycle: daytime + night as typed = 45 + 15 = 60 = CycleMinutes, nothing to adjust -> cycle 60 real min = daytime 45 + night 15
  2 share    : daylight share f = daytime / cycle = 45 / 60 = 0.75 (vanilla 0.7)
  3 rate     : ProductionBasis RealTime: requested clock rate R0 = ProductionScale = 1 game-seconds per real second (vanilla 1)
  4 day      : day length L = round(R0 x 60 x cycle) = round(1 x 60 x 60) = 3600 game-seconds (vanilla 1800) -> EnvMan.m_dayLengthSec on every machine
  5 clock    : exact clock rate R = L / (60 x cycle) = 3600 / 3600 = 1 game-seconds per real second -> ZNet.UpdateNetTime adds dt x R on every machine
  6 band     : sunrise at raw day-fraction 0.5 - f/2 = 0.125, sunset at 0.5 + f/2 = 0.875 (vanilla 0.15 / 0.85) -> EnvMan.RescaleDayFraction, GetMorningStartSec and SkipToMorning on every machine
  check      : daylight = f x L = 2700 game-s, at R that is 45 real min; night = 900 game-s = 15 real min; full day = 3600 game-s = 60 real min
  production : 1x vanilla per real minute (= R; a vanilla day of work, 1800 game-s, takes 30 real min); 2x vanilla per game day (= L / 1800; one game day holds 2 vanilla days of growth); realised ProductionScale 1 (requested 1)
  sun        : 4 degrees per real minute by day (180 / daytime; vanilla 8.57), 12 by night (180 / night; vanilla 20); the sun's pace depends on the lengths only, never on ProductionScale
[Info   :DvergrAstrolabe] self-check: EnvMan.RescaleDayFraction answers with sunrise at raw 0.125 and sunset at 0.875, as set (1000 samples); EnvMan.m_dayLengthSec = 3600.

With VerboseLogging on, every sunrise and sunset is measured against its schedule, so the log proves the lengths by itself:

[Info   :DvergrAstrolabe] sunset, day 12 (dedicated server): daylight ran 45.00 real min (45 scheduled); night for the next 15 real min.
[Info   :DvergrAstrolabe] sleep: skipping from 46500 to the sunrise of day 13 at 47250 game-s (750 game-s in 12 real s).

Set ProductionBasis = GameDays and keep ProductionScale = 1. The day stays 1800 game-seconds forever, so the day counter and the time of day never move — at the price of production tracking game days instead of real minutes. Switch to RealTime whenever you want vanilla real-time production; the counter shifts once, and the log says by how much.

• Players need the mod now. That is the whole change for them.
• Your settings carry over. On first start, an old DayMinutes + NightMinutes become CycleMinutes (their sum), DaytimeMinutes and NightMinutes, with ProductionBasis = GameDays — which keeps the 1800-second day, the per-day economy and your world's day counter. The log says so. The old keys stay in the file, ignored; delete them when you like.
• One visible difference: the old line paced daylight and night at two different clock rates inside vanilla's sunrise and sunset; this one moves sunrise and sunset and runs one flat rate. Production is the same per day and now even across it. The sun's position shifts once.
• The old limits are gone: no pausing near boats, no catch-up afterwards, no schedule slip on a server where someone is always sailing, no fast-day/slow-night contrast, no 0.2x floor. The settings that managed them are gone with them.
• Crossplay players still need the server-only line; the CHANGELOG lists its last version.