fix timestamps

lib/CleanPlugin.js

@@ -180,7 +180,7 @@ const applyDiff = (fs, outputPath, dry, logger, diff, isKept, callback) => {
 			switch (type) {
 				case "check":
 					if (isKept(filename)) {
-						keptAssets.set(filename, Date.now());
+						keptAssets.set(filename, 0);
 						// do not decrement parent entry as we don't want to delete the parent
 						log(`${filename} will be kept`);
 						return process.nextTick(callback);
@@ -365,7 +365,7 @@ class CleanPlugin {
 					if (assetInfo && assetInfo.hotModuleReplacement) {
 						currentAssets.set(normalizedAsset, now + _10sec);
 					} else {
-						currentAssets.set(normalizedAsset, now);
+						currentAssets.set(normalizedAsset, 0);
 					}
 				}
 
@@ -394,13 +394,13 @@ class CleanPlugin {
 						logger,
 						diff,
 						isKept,
-						(err, notDeletedAssets) => {
+						(err, keptAssets) => {
 							if (err) {
 								oldAssets = undefined;
 							} else {
 								if (oldAssets) mergeAssets(currentAssets, oldAssets);
 								oldAssets = currentAssets;
-								if (notDeletedAssets) mergeAssets(oldAssets, notDeletedAssets);
+								if (keptAssets) mergeAssets(oldAssets, keptAssets);
 							}
 							callback(err);
 						}