UFO sighting? Unbelievable expierience!

Late afternoon, after dinner my boyfriend and I went for a drive.  We would go to Mt. Peter and enjoy the view.  My companion and I looked ahead at the view,and a bright light appeared in the sky.  It was so bright, white hot and it pulsed on and off.  It continued to do this for about 2 minutes and then moved in a diagonal trajectory, continuing to pulse in a out of visibility.  
It was still daylight. I asked my boyfriend if he could see it and he said he did. I asked if he knew what it was and he said he did not.  After moving in an extemely precise diagonal it began to grow smaller as it pulsed in and out of view, until it finally disappeared. 
I've never forgotton the incident.  My former companion became less and less willing to discuss it.  I've long since moved to within a mile of it.  I'm not sure that is why... but I'm not sure it isn't!  
I can still remember it vividly.  I recall being to afraid to exit the vehicle but thinking about it.  I do recall feeling the technology of what I was witnessing was extemely advanced.
Witness indicates that the date of the incident is approximate.  PD