shouldn't use mod(%) operator.

shouldn't divide hour and then divide day again.
should use substring.
should split into 8 instead of 6.

src/module/timeLabel.js

@@ -1,5 +1,6 @@
 import moment from 'moment';
-const NUM_OF_PARTS_TO_SPLIT = 6;
+const NUM_OF_PARTS_TO_SPLIT = 8;
+const TOFIXED_DEICMAL = 1;
 
 /**
  * 若想要有等差的Y軸刻度，則必須確保index是乘以一個共通的被乘數
@@ -10,8 +11,10 @@ const NUM_OF_PARTS_TO_SPLIT = 6;
 export const getStepSizeOfYTicks = (maxTimeInSecond) => {
   const numOfParts = NUM_OF_PARTS_TO_SPLIT;
   const {unitToUse, timeValue} = getTimeUnitAndValueToUse(maxTimeInSecond);
+  console.log('{unitToUse, timeValue}', unitToUse, timeValue); // TODO:
   let resultStepSize;
-  resultStepSize = Math.floor(timeValue / numOfParts);
+  resultStepSize = (timeValue / numOfParts);
+  console.log('resultStepSize', resultStepSize); //TODO:
 
   return {resultStepSize, unitToUse};
 }
@@ -26,25 +29,29 @@ const getTimeUnitAndValueToUse = (secondToDecide) => {
   const hour = 60 * 60;
   const minutes = 60;
   const dd = secondToDecide / day;
-  const hh = (secondToDecide % day) / hour;
+  const hh = secondToDecide / hour;
-  const mm = (secondToDecide % hour) / minutes;
+  const mm = secondToDecide / minutes;
 
-  if (dd > 0 && dd > 1) {
+  if (dd > 0) {
+    console.log('dd > 0 && dd > 1 secondToDecide / day', secondToDecide / day); //TODO:
     return {
       unitToUse: "d",
       timeValue: secondToDecide / day,
     };
-  } else if (hh > 0 && hh > 1) {
+  } else if (hh > 0) {
+    console.log('hh > 0 && hh > 1 secondToDecide / hour', secondToDecide / hour);
     return {
       unitToUse: "h",
-      timeValue: (secondToDecide % day) / hour,
+      timeValue: secondToDecide / hour,
     };
-  } else if (mm > 0 && mm > 1) {
+  } else if (mm > 0) {
+    console.log('mm > 0 && mm > 1', secondToDecide / minutes);
     return {
       unitToUse: "m",
-      timeValue: (secondToDecide % hour) / minutes,
+      timeValue: secondToDecide / minutes,
     };
   } else {
+    console.log('less than one minutes final case timeValue:', secondToDecide, dd, hh, mm); //TODO:
     return {
       unitToUse: "s",
       timeValue: secondToDecide,
@@ -61,7 +68,10 @@ const getTimeUnitAndValueToUse = (secondToDecide) => {
  * @param {string} unitToUse time unit to display; "dhms" usually
  */
 export function getYTicksByIndex(stepSize, index, unitToUse){
-  return `${stepSize * index}${unitToUse}`;
+  const rawStepsizeMultIndex = (stepSize * index).toString();
+  const shortenStepsizeMultIndex = rawStepsizeMultIndex.substring(
+    0, rawStepsizeMultIndex.indexOf('.') + 1 + TOFIXED_DEICMAL);
+  return `${shortenStepsizeMultIndex}${unitToUse}`;
 };
 
 /**
@@ -263,9 +273,7 @@ export function dateLabel(date, maxDate, minDate) {
  * @returns {string} - The suitable time format string.
  */
 export const setTimeStringFormatBaseOnTimeDifference = (minTimeStamp, maxTimeStamp) => {
-  const laterDate = new Date(maxTimeStamp);
+  const timeDifferenceInSeconds = maxTimeStamp - minTimeStamp;
-  const earlyDate = new Date(minTimeStamp);
-  const timeDifferenceInSeconds = (laterDate - earlyDate);
 
   let dateFormat;
   if (timeDifferenceInSeconds < 60) {