From 7ecfc17f9df39859b340c8ba81c3c27bfb5f18ac Mon Sep 17 00:00:00 2001
From: Mindo Choi <141867620+apchoiCMD@users.noreply.github.com>
Date: Fri, 26 Apr 2024 18:25:52 -0400
Subject: [PATCH] Using ioda util to convert the datetime in AMSR2 converter
 (#1077)

#### This PR includes:
- Replace the method to get datetime from epoch time by using `ioda
utils`
- `julianDate - 2440588` will make half day off
- The above method will avoid dealing with decimal precision.
- Closes #1062

---------

Co-authored-by: Guillaume Vernieres <guillaume.vernieres@noaa.gov>
---
 utils/obsproc/IcecAmsr2Ioda.h | 38 ++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/utils/obsproc/IcecAmsr2Ioda.h b/utils/obsproc/IcecAmsr2Ioda.h
index 681bbcd8d..3241d3ae2 100644
--- a/utils/obsproc/IcecAmsr2Ioda.h
+++ b/utils/obsproc/IcecAmsr2Ioda.h
@@ -13,8 +13,10 @@
 
 #include <Eigen/Dense>    // NOLINT
 
+#include "ioda/../../../../core/IodaUtils.h"
 #include "ioda/Group.h"
 #include "ioda/ObsGroup.h"
+
 #include "oops/util/dateFunctions.h"
 
 #include "NetCDFToIodaConverter.h"
@@ -83,22 +85,34 @@ namespace gdasapp {
         int minute =  oneTmpdateTimeVal[i+4];
         int second = static_cast<int>(oneTmpdateTimeVal[i+5]);
 
-        // Replace Fillvalue -9999 to 0 to avoid crash in dateToJulian
+        // Avoid crash util in ioda::convertDtimeToTimeOffsets
         if (year == -9999 || month == -9999 || day == -9999 ||
           hour == -9999 || minute == -9999 || second == -9999) {
           year = month = day = hour = minute = second = 0;
         }
 
-        // Convert a date to Julian date
-        uint64_t julianDate = util::datefunctions::dateToJulian(year, month, day);
-
-        // Subtract Julian day from January 1, 1970 (convert to epoch)
-        int daysSinceEpoch = julianDate - 2440588;
-
-        // Calculate seconds only from HHMMSS
-        int secondsOffset = util::datefunctions::hmsToSeconds(hour, minute, second);
-
-        iodaVars.datetime_(index) = static_cast<int64_t>(daysSinceEpoch*86400.0f) + secondsOffset;
+        // Construct iso8601 string format for each dateTime
+        std::stringstream ss;
+        ss << std::setfill('0')
+           << std::setw(4) << year << '-'
+           << std::setw(2) << month << '-'
+           << std::setw(2) << day << 'T'
+           << std::setw(2) << hour << ':'
+           << std::setw(2) << minute << ':'
+           << std::setw(2) << second << 'Z';
+        std::string formattedDateTime = ss.str();
+        util::DateTime dateTime(formattedDateTime);
+
+        // Set epoch time for AMSR2_ICEC
+        util::DateTime epochDtime("1970-01-01T00:00:00Z");
+
+        // Convert Obs DateTime objects to epoch time offsets in seconds
+        // 0000-00-00T00:00:00Z will be converterd to negative seconds
+        int64_t timeOffsets
+           = ioda::convertDtimeToTimeOffsets(epochDtime, {dateTime})[0];
+
+        // Update datetime Eigen Arrays
+        iodaVars.datetime_(index) = timeOffsets;
         index++;
       }
 
@@ -106,7 +120,7 @@ namespace gdasapp {
       for (int i = 0; i < iodaVars.location_; i++) {
         iodaVars.longitude_(i) = oneDimLonVal[i];
         iodaVars.latitude_(i) = oneDimLatVal[i];
-        iodaVars.obsVal_(i) = static_cast<float>(oneDimObsVal[i]*0.01f);
+        iodaVars.obsVal_(i) = static_cast<float>(oneDimObsVal[i]*0.01);
         iodaVars.obsError_(i) = 0.1;  // Do something for obs error
         iodaVars.preQc_(i) = oneDimFlagsVal[i];
         // Store optional metadata, set ocean basins to -999 for now