The date question is perhaps best covered by Timothy Good in his Alien Base book (1998), to quote: “Another of my questions dealt with the fact that, in all editions of his first book, The White Sands Incident (first published in 1954), the date of the incident is given as 4 July 1950. Yet 10 years after publication he admitted that the incident actually occurred on July 4th, 1949.

” ‘I had to change it,’ he explained. ‘In the last edition [1966], I told the publisher to change it, but he decided this might not be a good for publicity, and he kept it to 1950 after I’d said to change it, because there was now no need to hide the fact that it was 1949.’

” ‘So there was a reason?’ I asked.

” ‘There was a reason,’ Dan replied, ‘because it turned out to be a year later then he had originally planned – that Alan could be here.  He thought it could be done in four years; it actually took five years.  Now, had the Pentagon, for example, taken this book seriously, at the time there was a pretty good chance they could have tracked him down.  There had to be an escape mechanism.  The fact is that on the evening of the Fourth of July 1950, I was not at White Sands – I didn’t arrive there until later in July.  And everyone at White Sands Proving Grounds and in Aerojet knows that.'”

However, Dan was not very consistent with the decision to change the date it occurred on because even in 1989, when he gave a talk at a MUFON conference, he stated it occurred in 1949.  Also during a question and answer period while in Puerto Rico in 1983, Daniel said it was actually 5 years before he went public, as mentioned in this clip:

Conclusion: At this point, we really only have Daniel’s word and to back it up, it would be necessary to find Aerojet employees or White Sands people who could collaborate his statement.  Until then, who knows…