Delay is 50ms on my MBP. Here is a profile: <a href="http:&#x2F;&#x2F;i.imgur.com&#x2F;ty11Utl.png" rel="nofollow">http:&#x2F;&#x2F;i.imgur.com&#x2F;ty11Utl.png</a><p>With the main bottleneck being here: <a href="https:&#x2F;&#x2F;github.com&#x2F;BelkaLab&#x2F;react-yearly-calendar&#x2F;blob&#x2F;master&#x2F;src&#x2F;Calendar.js#L56-L82" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;BelkaLab&#x2F;react-yearly-calendar&#x2F;blob&#x2F;maste...</a><p>Implementing a good shouldComponentUpdate() should fix it.