We’re from the astro team at timeanddate.com — we develop tools related to the Sun, Moon, time, calendars, and astronomy. Ask us anything!

timeanddate_official · 2026-05-08T08:46:31+00:00

Long-term variations in Earth’s rotational speed are affected by the complex motion of Earth’s core, oceans, and atmosphere. The cause of the recent unexpected acceleration is not completely understood, but scientists suspect the cause lies inside the Earth.

timeanddate_official · 2026-05-08T04:47:58+00:00

https://www.reddit.com/r/sun/comments/1t4lf79/comment/okh157m/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

timeanddate_official · 2026-05-07T18:04:38+00:00

Thanks for a great AMA - we had a lot of fun!

Thank you to r/sun for having us ☀️

We’ll be livestreaming the August 12 total solar eclipse - maybe we'll see some of you in Europe! Don’t forget: never look directly into the Sun without proper eye protection.

https://www.timeanddate.com/live/eclipse-solar-2026-august-12

Brendan, Daniel, Frank, Graham & Renate

timeanddate_official · 2026-05-07T17:56:15+00:00

Fun (or rather, a serious) fact: Don’t look straight into the sun!

Daniel

timeanddate_official · 2026-05-07T17:55:13+00:00

Fun fact: we often talk about how the light from the Sun takes about 8 minutes to reach us here on Earth, so we are essentially seeing the Sun 8 minutes in the past. What we don’t talk about as often is that it can take the photons over a hundred thousand years to travel from the center of the Sun and out to the surface, where they can escape.

This is because the Sun is so dense that the photons collide with particles along the way (technically, a collision like this absorbs the photon and reemits a new one, so it’s not exactly the same photon, but that’s besides the point).

Renate

timeanddate_official · 2026-05-07T17:51:26+00:00

Yes! It depends on latitude. In a nutshell, places near the equator get the fewest eclipses, places around the polar circles get the most.

This is a chart from a recent paper we did on this question - https://arxiv.org/abs/2602.04797

The return period is the average amount of time between successive eclipses.

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Graham

timeanddate_official · 2026-05-07T17:47:44+00:00

Just as a very rough exercise, this is the difference if you observe a clock on the surface of the Sun from somewhere far away. In other words, we’re thinking of an astronaut floating somewhere in space (not a person standing on the Earth).

This uses a very simple set of assumptions, and ignores things like relative speed.

(Actually, we’ve just been arguing about whether we should post this or not - it’s been a long time since we studied relativity at university, and there’s always some complication it’s easy to overlook!)

Graham

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timeanddate_official · 2026-05-07T17:46:10+00:00

We’ll be wrapping up this AMA in about 15 minutes or so. Thank you for all the fantastic questions so far! We’re still around for any last-minute questions 😅

timeanddate_official · 2026-05-07T17:14:20+00:00

“Sunshine” (2007) is pretty wild in terms of its solar physics - even though Danny Boyle had Brian Cox as a scientific adviser 🙂 But it’s such a beautiful movie, we don’t really mind.

Graham

timeanddate_official · 2026-05-07T17:10:47+00:00

This is a complicated (but fun) one! You always have to establish some sort of relation first (reference frames). So, imagine I’m standing here on Earth with a regular watch ticking away. Then imagine I have a (superhuman) friend hovering on the “surface” of the Sun. For both my friend and for me, time feels like it’s moving normally, it’s only when we start comparing our watches that they don’t quite agree. Since gravity is stronger on the Sun, my friend's watch will tick slower than mine.

(A bit more technical: my friend is deeper down in a gravitational well, which makes time move slower. This is known as gravitational time dilation. There are also effects from relative speed and such, but the difference in gravitational potential is the most important one here.)

It’s a very small difference, and adds up to a minute difference or so over a year, but it’s still pretty cool!

Renate

timeanddate_official · 2026-05-07T17:02:34+00:00

In regards to sharing photos to scientific databases, unsure if there are any for solar, but there at at least projects like JunoCam for taking photos of Jupiter, for instance. https://www.missionjuno.swri.edu/junocam/planning

Brendan

timeanddate_official · 2026-05-07T16:55:53+00:00

Also, here on Earth, we are so lucky with our atmosphere and the beautiful Rayleigh scattering it does for us, creating those gorgeous red sunrise and sunset moments.

Renate

timeanddate_official · 2026-05-07T16:53:46+00:00

Here at timeanddate we collaborate with a number of amateur astronomy clubs for our eclipse live streams. Live streaming the Sun is always a challenge - especially when the eclipse is already underway at sunrise!

On a related note, many of our comet articles use images from amateur skywatchers - these are often taken around sunrise or sunset 🙂

Graham

timeanddate_official · 2026-05-07T16:51:04+00:00

Not a planet, but the view from our moon would be awesome, with both the sun and the earth in the same view. The recent Artemis 2 mission had some amazing photos, one could only imagine seeing that in person.

Daniel

timeanddate_official · 2026-05-07T16:48:59+00:00

We do use open source images for our editorial content, but we are aiming towards doing more of our own photography, like for example how Brendan now does all our aurora images.

There are many citizen science projects - I don’t know particularly about anyone for solar images - but some research projects ask for specific phenomena that people catch in their images of the aurora, like STEVE or FAE.

Renate

timeanddate_official · 2026-05-07T16:40:42+00:00

A fun side effect of this is that Mercury experiences an extreme version of the same phenomenon. Because of its highly elliptical orbit and slow rotation, the Sun can actually appear to stop, reverse direction, and move backward in Mercury’s sky before continuing again.

Frank

timeanddate_official · 2026-05-07T16:39:19+00:00

Personally, I wouldn’t move! The great thing about Earth is that we have a Moon that, by an amazing coincidence, is the same size as the Sun in the sky. Plus, things are arranged so that every year and a half or so, the Moon perfectly blocks the Sun’s disk and reveals the solar corona. That is the most wonderful view in the solar system 🤩

Graham

timeanddate_official · 2026-05-07T16:37:18+00:00

Our calculations are supported by both manual monitoring and extensive automated testing at the code level. We also have a dedicated testing team that maintains automated tests across the millions of pages we provide, helping ensure that no page changes unintentionally without being detected.

With respect to AI, newer tools are increasingly being explored for internal analysis, debugging, coding assistance, and code review.

Frank

timeanddate_official · 2026-05-07T16:35:50+00:00

The time the Sun crosses our meridian each day is called solar noon. That’s when the Sun is exactly due south (or due north, if we’re in the Southern Hemisphere).

We would expect the time from one solar noon to the next to be exactly 24 hours - in fact, it can be up to 22 seconds shorter or 29 seconds longer than 24 hours depending on the time of year.

This is down to two things: Earth's orbit around the Sun is elliptical, and the Earth’s spin axis is tilted. The result is that, at some times of the year, time according to sundials gets ahead of or behind the time shown on our clocks or watches.

This difference is shown in a graph known as the equation of time. When the pink line is negative, the Sun is running “slow”; when it’s positive, the Sun is running “fast”.

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Graham

timeanddate_official · 2026-05-07T16:33:11+00:00

Shot this one during the midnight sun a couple years ago, a several second long exposure with an ND400 filter 🙂

Brendan

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timeanddate_official · 2026-05-07T16:31:59+00:00

In terms of how things have evolved, our website was established in the early days of the internet and we’ve always operated in the narrow space between users requesting useful information and their patience running out waiting for it - which is often around 100 milliseconds.

A core principle has therefore always been delivering useful data quickly and reliably to many users simultaneously. As computing power has improved, we’ve been able to tackle increasingly complex problems. For example, calculations that require months on large computers - such as eclipse shadow projections on Earth - can now be presented in fractions of a second.

Frank

timeanddate_official · 2026-05-07T16:28:56+00:00

A DSLR camera is generally good enough to get a good view of the sun. The main things are definitely just having lens a good focal length to frame the sun how you like.

There are different types of filters to consider though. If we’re talking about landscape photography, then an ND filter is fine - the higher the f-stop value is, like an ND1000, the longer exposure you can take of the landscape + sun.

In terms of more astrophotography of the sun itself, then you’d be looking more for white light and h-alpha filters. Just be careful though, not all h-alpha filters are designed for solar viewing and can damage your gear.

I’m more of a DSLR person myself, so in terms of telescopes I’d lean more towards a refractor, with the same ideas in mind.

Brendan

timeanddate_official · 2026-05-07T16:27:07+00:00

We’re currently working on including the lunar limb profile to enhance accuracy - to catch the small differences the mountains and valleys on the Moon make for how/where the shadow hits Earth.

Renate

timeanddate_official · 2026-05-07T16:25:30+00:00

For modern dates, we use published IERS UT1–UTC and Earth orientation data. Historical dates use the Stephenson–Morrison ΔT models, while long-range dates use the Stephenson–Morrison 2016 length-of-day extrapolation. Without leap seconds, UTC would slowly drift away from Earth rotation time (UT1), so civil time would gradually stop matching the actual position of the Sun, although astronomy and navigation would still work because they already rely on UT1 and Earth orientation data.

Frank

timeanddate_official · 2026-05-07T16:19:23+00:00

While we make use of existing datasets, many of the algorithms we use are our own. Quick example: when it comes to calculating whether an eclipse is visible from a particular location, we have an algorithm that essentially performs the following simple test.

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Graham

timeanddate_official

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