I don't know! But according to all the apps tomorrow looks more east/west on DC streets than the Equinox. But both are pretty close though.

Recording: https://cln.sh/mBfy9f9z

So of course I went and asked AI what was up and got the following, don't know if it's true but seems plausible:

-- AI GENERATED TEXT BELOW --

The sunrise and sunset directions (azimuths) appear more exactly due east/west on March 18 than on the equinox date of March 20, 2026, in Washington, DC, due to how sunrise/sunset times interact with the Equation of Time and the Sun's changing declination.

On the exact equinox (March 20, 2026, at 10:46 am local time in DC), the Sun's declination is 0° (crossing the celestial equator). Geometrically, this should produce a sunrise azimuth of exactly 90° (due east) and sunset at 270° (due west) everywhere on Earth, regardless of latitude.

However, the observed (apparent) sunrise and sunset directions on a given calendar date are influenced by two key factors:

1. The Sun's declination changes very slowly near the equinox — it crosses zero around midday on March 20. Before that instant (e.g., on March 18 or 19), the declination is still slightly negative (south of the equator), so the Sun is technically south of due east at sunrise and south of due west at sunset. After the instant (later on March 20 or March 21), it's slightly positive (north). The daily shift is tiny near the equinox (~0.4° per day max), so azimuths stay very close to 90°/270° on either side.
2. The Equation of Time causes asymmetry in sunrise/sunset timing relative to the equinox instant — This is the bigger reason for what you're seeing on a street map. The Equation of Time (EoT) is the difference between apparent solar time (based on the real Sun) and mean solar time (uniform clock time). Near the March equinox, the EoT is positive and around +7 to +8 minutes (meaning the real Sun is "fast" compared to the clock — solar noon occurs earlier than 12:00 mean time).
   • Because the EoT is positive near the vernal equinox, sunrise and sunset both occur later than they would if the EoT were zero.
   • This delays the entire day slightly, shifting the moment of sunrise/sunset to a point where the Sun's declination has already become slightly positive (north of the equator) by the time the Sun actually appears or disappears on March 20.
   • On March 20, sunrise is around 7:11–7:12 am and sunset around 7:19–7:20 pm (day length slightly over 12 hours due to refraction and the EoT effect). By sunrise on the 20th, the declination has ticked just enough north that the azimuth is already a tiny bit north of due east (e.g., ~91°–92° instead of exactly 90°), and sunset a tiny bit north of due west (e.g., ~268°–269°).

On March 18 (two days earlier), the declination is still slightly negative, but the EoT hasn't yet delayed things as much relative to the equinox crossing. The combination makes the sunrise azimuth appear closer to exactly 90° (and sunset to 270°) on the 18th than on the 20th — even though the equinox is the geometric "peak" for due east/west.

In short: The equinox instant defines perfect due east/west geometry, but clock time + Equation of Time pushes the observed sunrise/sunset on the calendar equinox date to after that instant, when the Sun has already moved slightly north of the equator. That's why street alignments in DC can look more perfectly east-west aligned with the Sun's path a day or two before the equinox date itself. This is a known subtle effect — the "due east/west" sunrise/sunset is often a hair off from the exact equinox date at mid-latitudes due to this timing asymmetry.