When is the next "double-13 Friday"?

[Henry]

Jon Wild wrote:

> On Sat, 14 Oct 2006, Joshua Zucker wrote:
>
>> On 10/14/06, Jon Wild <wild at music.mcgill.ca> wrote:
>>
>>> I don't think your conjecture is correct, because I remember working 
>>> out
>>> once that the 13th falls more often on a Friday than on any other 
>>> day of
>>> the week. (This is possible because the whole 400-year cycle of the
>>> calendar contains a number of days that is not a multiple of 7.) So the
>>> number of Thursday-the-13ths, Wednesday-the-13ths, etc., per year 
>>> cannot
>>> follow the same pattern as the number of Friday-the-13ths per year.
>>
>> I think everything Jon Wild writes above is correct except for the
>> word "not" just preceding the "a multiple of 7".  That is, the 13th
>> falls more often on a Friday because the whole 400 year cycle of the
>> calendar contains a number of days that IS a multiple of 7.
>
> D'oh! Thanks Joshua, that's exactly what I meant.

Perhaps: This is possible because the whole 400-year cycle of the
calendar contains a number of days [146097] that is a multiple of 7 but 
not a multiple of 49.