We may have atomic clocks which then give us GPS time. We may have leap-seconds every few years, but our everyday clock is the Sun.
My plan was to photograph the Sun at 34 minutes past the hour throughout the day and then make a panorama of it across the sky. I am 8.5 degrees west and although we are at GMT (UTC) we also have summertime, so the Sun's "noon: would be at 13:34.
So - up bright and early. Trudge out into the field every hour - but the weather would not cooperate. I got clear skies in the morning but then a cloudy noon. I got a cloudy morning and sunny noon.
So - I settled for just these three shots of noon and an hour either side of it, which were actually shot on the 21st - the Summer Solstice :-)