The estimated time for your body to get into ketosis is estimated to be 1-3 days.  Although it can even extend up to 10 days  or more than a month  depending on how your nutrition was prior to starting the ketogenic diet.
The body enters ketosis when it switches using the primary energy source from glucose to ketones. 
 How long does it take to get into ketosis – Healthline
 How long does it take to get into ketosis – My Keto Kitchen