  T CrB is one of the most-famous and brightest novae known, and is a recurrent
nova with prior eruptions in 1866 and 1946 that peak at $V$=2.0. I have
constructed light curves spanning 1842--2022 with 213,730 magnitudes, where the
$B$ and $V$ magnitudes are fully corrected to the Johnson system. These light
curves first reveal a unique complex high-state (with 20$\times$ higher
accretion rate than the normal low-state) stretching from -10 to +9 years after
eruption, punctuated with a deep pre-eruption dip (apparently from dust
formation in a slow mass ejection) and a unique enigmatic secondary eruption
(with 10 per cent of the energy of the primary eruption), with the light curves
identical for the 1866 and 1946 eruptions. Starting in 2015, T CrB entered the
high-state, like in 1936, so a third eruption in upcoming years has been widely
anticipated. With the pre-1946 light curve as a template, I predict a date of
2025.5$\pm$1.3 for the upcoming eruption, with the primary uncertainty arising
from a possible lengthening of the pre-eruption high-state. I use the
large-amplitude ellipsoidal modulation to track the orbital phase of the binary
from 1867--2022. I measure that the orbital period increased abruptly by
$+$0.185$\pm$0.056 days across the 1946 eruption, the 1947--2022 years had a
steady period decrease of ($-$8.9$\pm$1.6)$\times$10$^{-6}$ days-per-day, and
the 1867--1946 years had a steady period change consistent with zero, at
($+$1.75$\pm$4.5)$\times$10$^{-6}$ days-per-day. These large period changes
cannot be explained by any published mechanism.
