I can slide those dates towards the end of the month, and avoiding leap years, get the age gap down to 19 days.
I think that’s the best one that includes the end of February in the date range.
You are getting pretty close but there are a few that have a smaller gap.
If anyone else wants to or is having a go at this teaser, it doesn’t need any fancy maths. Maybe a bit of lateral thinking to narrow it down. Well, that’s how I approached it.
With 24/02/48 and 16/03/48 I get a difference of 21 days.As Don is already at 19, I have to think a little more.
Well, I’ve now got it down to 16 days.
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16 is the best I can do too, so well done!
I think @Mulberry is getting there too.
As a follow-up, what is the largest gap between successive magic dates?
Waiting to pick up our daughter gave me an opportunity to ponder this teaser a little more. Without the need to avoid leap years et cetera I am down to 16 days now.
That’s great. Can you let us know the dates you found?
Sure, I wanted to keep the answer vague at first, to give others some more time. My best solution is 30/01/30 and 15/02/30.
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Same dates as I found. and I quoted 16 for the same reason.
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Assuming the reference to “couples” no longer applies, I have two dates that are just a “few” days shy on a century.
By a “few” i’m talking something like 62 days shy of a century
Are they successive magic dates, that is with no others in between?
Ah ! Got focused on the largest possible spread of dates rather than the largest gap between successive dates.
Must learn to read !
My plan at present is 
There are no magic dates in those years from 1932 onwards with prime numbers in the last two digits eg 1937.
I’m looking at late dates in the previous year and early dates in the following year.
At the moment I have a provisional (*) period of 583 days between consecutive Magic Dates, but this might not be the largest gap to be found.
(*) ie I have to check and count the days more carefully.
I have to read and grade some bad exam papers in the next few days. If I need to get my head straight, I might tackle that teaser.
Hi Mulberry, I’m still working through a few options. All subject to review and check. I have a couple that exceed 1,000 days.
But like you, I have other priorities needing my attention.
Following a quick review and check, I now only have one option that exceeds 1,000 days.
I’ll have another review and check this evening, hopefully.
There are a few periods of interest where a Prime Year is preceded or succeeded by a year that has only two factors eg 61 is Prime and 62 only has factors of 2 and 31. There are only 28 days in Feb 62 so 1962 doesn’t have any Magic Dates. Neither does 61. Even so, this option only generates an 836 day gap (subject to check - it’s too easy to count days in the wrong direction !)
I’ll also re-check my >1,000-day solution which follows the 61/62 principle.
At the moment the largest gap that I can find between consecutive Magic Dates is 3 years and 1 day.
This equates to 1097 days because one of the years is a leap year.
I’ll leave it there for the moment, Mrs D keeps reminding me of other priorities …
A gap in the other priorities gave me a chance to review and check my options.
The best I can come up with is the 1097 days as mentioned above.
My strategy has been along the following lines ::
The 19th Century started 01/01/1901 and ended 31/12/2000
There will always be at least one Magic Date in the years 01 thru 31, ie in January.
There will be no Magic Dates in the years 32 onwards which are Prime
There will be at least one Magic Date in the Even-numbered years up to 56
Beyond 56, there are a few years where the factors are limited to 2 and a Prime. These are worth a careful look, especially when they are adjacent to a Prime Year.
That’s a summary of my thinking so far.
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I also arrived at 1097, but my approach was less methodical, so I didn’t manage to prove it was the maximum, so well done! Instead I resorted to using Excel to verify the maximum. A bit of a beast at 36,525 lines, but I have done worse!
I found it a bit easier to think through the logic for the shortest gap.