<p>I am trying to understand the lag of tides - in other words, how and why spring tides occur some time after full moon and new moon, and not at the time of the full/new moon (and similarly for neaps after the quarter moon).  To do that, I need to know when spring tides occur - the date and time.  Is it possible to state this?</p>
<p>My understanding is that a spring tide is defined as the tide with the largest range.  But sometimes more than one tide has the largest range - e.g., at Dover in January 2022 (I happen to have at hand the 2022 edition of Reeds Almanac, which contains the official UK Hydrographic Office tidal predictions), full moon was on 17th January, the highest HW was 6.5m which occurred on the 22nd and 23rd, the lowest LW was 1.2m which occurred on the 19th, 20th, 21st and 22nd, and the largest range was 5.2m which occurred on the 20th, 21st, 22nd and 23rd. So, when is the spring tide? Why does Reeds say it is on the 20th?</p>
<p>To know how long the lag is, it is necessary to know the time of the full moon and the times of the spring tide.  In the example above, full moon was at 2321 on 17th January.  So, if springs is at an unknown time on the 20th, the lag could be anything between just over 2 days to just over 3 days.  Is it possible to state the time of a spring tide, as well as its date, so that a more precise estimate of the lag can be made?</p>
<p>I am NOT asking about the time of high water at springs, which varies from place to place, but about the time at which tides all over the world are at their greatest.</p>

CC BY-SA 4.0
2024-09-27T17:48:07.820Z
Re "the time at which tides all over the world are at their greatest" Are you asking about [king tides](https://en.wikipedia.org/wiki/King_tide)?
njuffa
CC BY-SA 4.0
2024-09-27T18:08:03.010Z
I am not asking about king tides.
Steve Lenartowicz
CC BY-SA 4.0
2024-10-03T13:47:38.330Z
I think there are two slightly different questions buried in here:

The main one is about why the largest tides don't always align with full and new moons. The other is about which is called the "spring" tide when there are multiple candidates.
Semidiurnal Simon
<tides>
When exactly is a spring tide?
Steve Lenartowicz
# When exactly is a spring tide?

(Asked by: username_0 on 2024-09-26)

I am trying to understand the lag of tides - in other words, how and why spring tides occur some time after full moon and new moon, and not at the time of the full/new moon (and similarly for neaps after the quarter moon). To do that, I need to know when spring tides occur - the date and time. Is it possible to state this?

My understanding is that a spring tide is defined as the tide with the largest range. But sometimes more than one tide has the largest range - e.g., at Dover in January 2022 (I happen to have at hand the 2022 edition of Reeds Almanac, which contains the official UK Hydrographic Office tidal predictions), full moon was on 17th January, the highest HW was 6.5m which occurred on the 22nd and 23rd, the lowest LW was 1.2m which occurred on the 19th, 20th, 21st and 22nd, and the largest range was 5.2m which occurred on the 20th, 21st, 22nd and 23rd. So, when is the spring tide? Why does Reeds say it is on the 20th?

To know how long the lag is, it is necessary to know the time of the full moon and the times of the spring tide. In the example above, full moon was at 2321 on 17th January. So, if springs is at an unknown time on the 20th, the lag could be anything between just over 2 days to just over 3 days. Is it possible to state the time of a spring tide, as well as its date, so that a more precise estimate of the lag can be made?

I am NOT asking about the time of high water at springs, which varies from place to place, but about the time at which tides all over the world are at their greatest.

**Tags:** tides

> **Comments:**
> **username_1**: Re "the time at which tides all over the world are at their greatest" Are you asking about [king tides](https://en.wikipedia.org/wiki/King_tide)?  
> **username_0**: I am not asking about king tides.  
> **username_2**: I think there are two slightly different questions buried in here:  The main one is about why the largest tides don't always align with full and new moons. The other is about which is called the "spring" tide when there are multiple candidates.  

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