diff --git a/src/TimeGrid.js b/src/TimeGrid.js
index 79d991ac4..90e4029dd 100644
--- a/src/TimeGrid.js
+++ b/src/TimeGrid.js
@@ -382,7 +382,7 @@ export default class TimeGrid extends Component {
   calculateScroll(props = this.props) {
     const { min, max, scrollToTime, localizer } = props
 
-    const diffMillis = scrollToTime - localizer.startOf(scrollToTime, 'day')
+    const diffMillis = localizer.diff(localizer.merge(scrollToTime, min), scrollToTime, 'milliseconds')
     const totalMillis = localizer.diff(min, max, 'milliseconds')
 
     this._scrollRatio = diffMillis / totalMillis