fix: Fix the ledger_index timezone issue (#1522)

Fix unittest failures

src/util/TimeUtils.cpp

@@ -0,0 +1,42 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2024, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "util/TimeUtils.hpp"
+
+#include <xrpl/basics/chrono.h>
+
+namespace util {
+[[nodiscard]] std::optional<std::chrono::system_clock::time_point>
+SystemTpFromUTCStr(std::string const& dateStr, std::string const& format)
+{
+    std::tm timeStruct;
+    auto const ret = strptime(dateStr.c_str(), format.c_str(), &timeStruct);
+    if (ret == nullptr) {
+        return std::nullopt;
+    }
+    return std::chrono::system_clock::from_time_t(timegm(&timeStruct));
+}
+
+[[nodiscard]] std::chrono::system_clock::time_point
+SystemTpFromLedgerCloseTime(ripple::NetClock::time_point closeTime)
+{
+    return std::chrono::system_clock::time_point{closeTime.time_since_epoch() + ripple::epoch_offset};
+}
+
+}  // namespace util