Equation of time.

[Igel]

https://www.timeanddate.com/astronomy/equation-of-time.html

Want the math? ("Just say no.&quot Then there's a nifty Wiki article on it.

Always annoys my astro students when they come back to the classroom in early January and say that the days will be getting longer so sunrise will be earlier. (Currently it's way into first period and if I work too late I arrive in the dark and leave in the dark.) I disabuse them of the idea.

Basically, the time of solar noon (when the sun's at meridian) shifts earlier or later, predictably, during the year. Obliquity (tilt) and eccentricity ('how elliptical') blend together. Currently, it's shifting to later than clock 'noon'.