Nadivalaya Yantra a vertical sundial

Follows the sun between the northern and southern hemispheres.  From March 21st to September 23rd the sun is in the Northern hemisphere and from September to March in the Southern.  When one side of the instrument is in the sun the other identical side is in shadow.

It can also be used to ascertain International Standard Time

Jai Prakash Yantra

The most accurate of Jai Singh's instruments and the one which was used to verify the readings and calculations of all the others and make adjustments if necessary.

Samrat Yantra

The largest sundial in the world.  Calculates Jaipur time.  Before Indian Standard Time each town operated on its own time, accurate but out of step with other towns.

The gnomon stands 90' tall and has many windows to prevent storm  damage.  It is aligned north south and rises at an angle of 27 degrees.  As Jaipur is 27 degrees north the gnomon points toward the celestial pole.

At 6am the shadow of the gnomon falls on the top of the western quadrant some 50' away  As the sun raises higher it descends along the arc of the quadrant, until noon when time stands still.  But only momentarily, then the shadow begins it's climb of the eastern quadrant, until 6pm.  

Steps beside the arc of the quadrants enable the observer to climb up to take precise readings. The edge of the quadrants are graduated in hours, minutes and seconds.  Each minute being divided into 30 parts, making it accurate to within 2 seconds. 

It is even possible to tell the time at night by observing the position of a star from one of the quadrants and moving until the star touches to top of the gnomon.