In the first example, you have moved a prepositional phrase ("in 1965") to the beginning of the sentence. This is common and completely acceptable in English. Which one you should choose depends mainly on the context surrounding the sentence.
Here is an example where I would recommend the first version:
In 1965 the 'Snurfer' was developed as a child's toy. By 1967, it had become the best-selling toy of all time.
And here is an example where I would recommend the second version:
The 'Snurfer' was developed as a child's toy in 1965. Its low price and high versatility made it an instant hit.
Even though both examples communicate similar ideas, the first focuses on a sequence of chronological events while the second focuses on the qualities of the toy itself.
I initially thought that you were wrong to omit a comma after the prepositional phrase. In other words, I thought it should have been:
In 1965, the 'Snurfer' was developed as a child's toy.
But a little bit of research revealed that the rules for using commas this way are flexible. According to one guideline I found, you only need a comma if the phrase is four or more words long.
If you added more words, like in the following example, a comma would be required or highly recommended, depending on whom you ask.
In the summer of 1965, the 'Snurfer' was developed as a child's toy.