diff --git a/R/CST_MergeDims.R b/R/CST_MergeDims.R
index 6756ce7937adc9527aa8482c049f0c10b64951a8..bb06bf608051d06ecabce9a9cd3163c03128c6ad 100644
--- a/R/CST_MergeDims.R
+++ b/R/CST_MergeDims.R
@@ -53,8 +53,14 @@ CST_MergeDims <- function(data, merge_dims = c('ftime', 'monthly'),
 
   # attrs
   if (all(merge_dims %in% names(dim(data$attrs$Dates)))) {
+    original_timezone <- attr(data$attrs$Dates[1], "tzone")
     data$attrs$Dates <- MergeDims(data$attrs$Dates, merge_dims = merge_dims,
                                   rename_dim = rename_dim, na.rm = na.rm)
+    # Transform dates back to POSIXct
+    data$attrs$Dates <- as.POSIXct(data$attrs$Dates,
+                                   origin = "1970-01-01",
+                                   tz = original_timezone)
+
   } else if (any(merge_dims %in% names(dim(data$attrs$Dates)))) {
     warning("The dimensions of 'Dates' array will be different from ",
             "the temporal dimensions in 'data'. Parameter 'merge_dims' ",