Concept of circadian variation of BP has entered the clinical domain in 21st century. BP is highest in early to mid morning and falls progressively all through the day. BP is lowest at night nocturnal dip BP rises before waking morning surge . ABPM has consistently shown that the sleep time BP mean is a better predictor of CVD events like stroke MI SCD etc. than the daytime or 24 hour BP means. Modification of timing of the drug has immense effect in altering the cicardian rhythm 8594 converts non dippers to dippers J Am Soc Nephrol. 2011 Dec 22 12 2313 21 . RAAS blockers are classical agents and have been well tried to modify this physiological phenomenon where shifting from morning dose to evening dose is done Several of pathophysiologic systems responsible for the circadian BP variability especially salt balance and the RAAS can be modulated by appropriate long term therapy The physiological basis of the concept is so overwhelming that it has been appreciated by the Nobel committee this year to recognize three Physiologists with the Nobel Award in Medicine in 2017.