Are you guys sure? I see on the wikipedia list that Borg became number 1 on august 23rd 1977 and held that position for just 1 week.
to be fair, the only thing I know for sure is that on the ATP website, you can only see the full rankings updated weekly from the 25th of june 1984.
Whether or not it was calculated weekly before that, I'm not sure and I would be glad to know the answer,
but well can the guy who wrote that on Wikipedia be trusted either ? he may also have said that because he only saw Borg number 1 on the 23rd of august 1977 and then he saw nothing written for next weeks ... and then mis-interpreted it as "number 1 for one week" (besides it was just the week before the US Open, if he really had been number 1 only for one week, it would mean that Connors would have played and made a result the week before the US Open). I've seen so many mis-interpretations like that
McEnroe also got one week in 1980 - aug 11th. And there were five more "one-weekers" in 1982 and 1983, courtesy of Connors and McEnroe.
They did occasionally release rankings two or more weeks in a row, just not regularly.
your post makes me think even more that my interpretation of the "one week" note on wikipedia or tennis-x was just related to a mis-interpretation of what's written on the ATP website as I said.
An easy way to see if they were number 1 only for one week would be to see if there's another player who was actually said as ranked number 1 on the ATP website one week later or if there was just no ranking released.