diff --git a/inst/extdata/gh_issue_288.xlsx b/inst/extdata/gh_issue_288.xlsx
new file mode 100644
index 00000000..f1394610
Binary files /dev/null and b/inst/extdata/gh_issue_288.xlsx differ
diff --git a/src/write_file.cpp b/src/write_file.cpp
index 6df31be1..23334b0d 100644
--- a/src/write_file.cpp
+++ b/src/write_file.cpp
@@ -1,5 +1,6 @@
 
 #include "openxlsx.h"
+#include <regex>
 
 
 //' @import Rcpp
@@ -225,16 +226,21 @@ SEXP buildMatrixMixed(CharacterVector v,
         if(!notNAElements[ri]){
           datetmp[ri] = NA_REAL; //IF TRUE, TRUE else FALSE
         }else{
-          // dt_str = as<std::string>(m(ri,i));
           dt_str = m(ri,i);
+
           try{
-            datetmp[ri] = Rcpp::Date(atoi(dt_str.substr(5,2).c_str()), atoi(dt_str.substr(8,2).c_str()), atoi(dt_str.substr(0,4).c_str()) );
-          }catch(...) {
+            // Some values are incorrectly detected as dates. This regex determines if they are numerics.
+            // If so, they are converted to Dates. 
+            Rcpp::Function cTD("convertToDate");
+            if (std::regex_match( dt_str, std::regex( ( "((\\+|-)?[[:digit:]]+)(\\.(([[:digit:]]+)?))?" ) ) )) {
+              datetmp[ri] = as<Rcpp::Date>(cTD(dt_str));
+            } else {
+              datetmp[ri] = Rcpp::Date(atoi(dt_str.substr(5,2).c_str()), atoi(dt_str.substr(8,2).c_str()), atoi(dt_str.substr(0,4).c_str()) );
+            }
+          } catch(...) {
             Rcpp::Rcerr << "Error reading date:\n" << dt_str << "\nrow: " << ri+1 << "\ncol: " << i+1 << "\n";
             throw;
           }
-          //datetmp[ri] = Date(atoi(m(ri,i)) - originAdj);
-          //datetmp[ri] = Date(as<std::string>(m(ri,i)));
         }
       }
       
diff --git a/tests/testthat/test-date_time_conversion.R b/tests/testthat/test-date_time_conversion.R
index ab2e4e11..23307cae 100644
--- a/tests/testthat/test-date_time_conversion.R
+++ b/tests/testthat/test-date_time_conversion.R
@@ -33,3 +33,21 @@ test_that("convert to datetime", {
   x_datetime <- convertToDateTime(x, tx = "UTC")
   attr(x_datetime, "tzone") <- "UTC"
 })
+
+
+
+test_that("read.xlsx detectDates", {
+  
+  xlsxFile <- system.file("extdata", "gh_issue_288.xlsx", package = "openxlsx")
+  
+  ref_dat <- data.frame(Date = c(as.Date(c("2021-10-20", "2021-11-03"))))
+  ref_num <- data.frame(Date = c(44489.4, 44503.0))
+  
+  tst_dat <- read.xlsx(xlsxFile, detectDates = TRUE)
+  tst_num <- read.xlsx(xlsxFile, detectDates = FALSE)
+  
+  expect_equal(ref_dat, ref_dat)
+  expect_equal(ref_num, ref_num)
+  
+})
+ 
\ No newline at end of file