diff --git a/ObservationSim/Config/Header/ImageHeader.py b/ObservationSim/Config/Header/ImageHeader.py
index 6b71d5c7552969dff93045f7eab4be2d767abc58..cd022b53633e5cfbef44601ae540a625037620b2 100644
--- a/ObservationSim/Config/Header/ImageHeader.py
+++ b/ObservationSim/Config/Header/ImageHeader.py
@@ -352,7 +352,7 @@ def generatePrimaryHeader(xlen = 9216, ylen = 9232, pointNum = '1', ra = 60, dec
     # ccdnum = str(k)
 
     datetime_obs = datetime.utcfromtimestamp(time_pt)
-    datetime_obs = datetime_obs.replace(microsecond=round(datetime_obs.microsecond, -5))
+    datetime_obs = datetime.utcfromtimestamp(np.round(datetime_obs.timestamp(), 1))
     # date_obs = datetime_obs.strftime("%y%m%d")
     # time_obs = datetime_obs.strftime("%H%M%S%f")[:-5]
 
@@ -558,9 +558,11 @@ def generateExtensionHeader(chip, xlen = 9216, ylen = 9232,ra = 60, dec = -40, p
     # t_s2 = str(tend_read.datetime).split()
     # h_ext['ROTIME1'] = t_s2[0] + 'T' + t_s2[1]
 
-    tstart1=tstart.datetime.replace(microsecond=round(tstart.datetime.microsecond, -5))
+    # tstart1=tstart.datetime.replace(microsecond=round(tstart.datetime.microsecond, -5))
+    tstart1 = datetime.utcfromtimestamp(np.round(datetime.utcfromtimestamp(tstart.unix).timestamp(), 1))
     h_ext['ROTIME0'] = tstart1.strftime("%Y-%m-%dT%H:%M:%S.%f")[:-5]
-    tend_read1 = tend_read.datetime.replace(microsecond=round(tend_read.datetime.microsecond, -5))
+    # tend_read1 = tend_read.datetime.replace(microsecond=round(tend_read.datetime.microsecond, -5))
+    tend_read1 = datetime.utcfromtimestamp(np.round(datetime.utcfromtimestamp(tend_read.unix).timestamp(), 1))
     h_ext['ROTIME1'] = tend_read1.strftime("%Y-%m-%dT%H:%M:%S.%f")[:-5]
     # h_ext['POS_ANG'] = pa
     header_wcs = WCS_def(xlen=xlen, ylen=ylen, gapy=898.0, gapx1=534, gapx2=1309, ra_ref=ra, dec_ref=dec, pa=pa, pixel_scale=pixel_scale, pixel_size=pixel_size,