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Add 12-hour datetime format parsing #118

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38c7d8b
initial working 12h datetime addition!!
hamzahchaudhry Jun 4, 2026
4786345
add ambigious handling + add tests
hamzahchaudhry Jun 4, 2026
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92 changes: 90 additions & 2 deletions src/Datetime.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,8 @@ bool Datetime::parse (
return true;
}

if (parse_formatted (pig, format))
bool ambiguous {false};
if (parse_formatted (pig, format, ambiguous))
{
// Check the values and determine time_t.
if (validate ())
Expand All @@ -176,6 +177,10 @@ bool Datetime::parse (
return true;
}
}
else if (ambiguous)
{
return false;
}

// Allow parse_date_time and parse_date_time_ext regardless of
// Datetime::isoEnabled setting, because these formats are relied upon by
Expand Down Expand Up @@ -232,7 +237,7 @@ void Datetime::clear ()
}

////////////////////////////////////////////////////////////////////////////////
bool Datetime::parse_formatted (Pig& pig, const std::string& format)
bool Datetime::parse_formatted (Pig& pig, const std::string& format, bool& ambiguous)
{
// Short-circuit on missing format.
if (format.empty ())
Expand All @@ -246,6 +251,8 @@ bool Datetime::parse_formatted (Pig& pig, const std::string& format)
int hour {-1};
int minute {-1};
int second {-1};
int meridiem {-1};
bool twelveHourTime {false};

// For parsing, unused.
int wday {-1};
Expand Down Expand Up @@ -353,6 +360,60 @@ bool Datetime::parse_formatted (Pig& pig, const std::string& format)
}
break;

case 'i':
twelveHourTime = true;
if (pig.getDigit (hour))
{
if (hour == 0)
pig.getDigit (hour);

if (hour == 1)
{
int tens = hour;
if (pig.getDigit (hour))
hour += 10 * tens;
}

if (hour < 1 || hour > 12)
{
pig.restoreTo (checkpoint);
return false;
}
}
else
{
pig.restoreTo (checkpoint);
return false;
}
break;

case 'I':
twelveHourTime = true;
if (! pig.getDigit2 (hour) || hour < 1 || hour > 12)
{
pig.restoreTo (checkpoint);
return false;
}
break;

case 'p':
if (compare (pig.peek (2), "AM", false))
{
meridiem = 0;
pig.skipN (2);
}
else if (compare (pig.peek (2), "PM", false))
{
meridiem = 1;
pig.skipN (2);
}
else
{
pig.restoreTo (checkpoint);
return false;
}
break;

case 'n':
if (pig.getDigit (minute))
{
Expand Down Expand Up @@ -539,6 +600,27 @@ bool Datetime::parse_formatted (Pig& pig, const std::string& format)
if (minute == -1) minute = 0;
if (second == -1) second = 0;

if (twelveHourTime && meridiem == -1)
{
ambiguous = true;
pig.restoreTo (checkpoint);
return false;
}

if (meridiem != -1)
{
if (hour < 1 || hour > 12)
{
pig.restoreTo (checkpoint);
return false;
}

if (meridiem == 0 && hour == 12)
hour = 0;
else if (meridiem == 1 && hour != 12)
hour += 12;
}

_year = year;
_month = month;
_day = day;
Expand Down Expand Up @@ -3394,6 +3476,9 @@ std::string Datetime::toString (const std::string& format) const
case 'V': formatted << std::setw (2) << std::setfill ('0') << week (); break;
case 'h': formatted << hour (); break;
case 'H': formatted << std::setw (2) << std::setfill ('0') << hour (); break;
case 'i': formatted << ((hour () % 12) == 0 ? 12 : (hour () % 12)); break;
case 'I': formatted << std::setw (2) << std::setfill ('0') << ((hour () % 12) == 0 ? 12 : (hour () % 12)); break;
case 'p': formatted << (hour () < 12 ? "AM" : "PM"); break;
case 'n': formatted << minute (); break;
case 'N': formatted << std::setw (2) << std::setfill ('0') << minute (); break;
case 's': formatted << second (); break;
Expand Down Expand Up @@ -3641,6 +3726,9 @@ int Datetime::length (const std::string& format)
case 'V':
case 'h':
case 'H':
case 'i':
case 'I':
case 'p':
case 'n':
case 'N':
case 's':
Expand Down
2 changes: 1 addition & 1 deletion src/Datetime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,7 @@ class Datetime

private:
void clear ();
bool parse_formatted (Pig&, const std::string&);
bool parse_formatted (Pig&, const std::string&, bool& ambiguous);
bool parse_named (Pig&);
bool parse_epoch (Pig&);
bool parse_date_time_ext (Pig&);
Expand Down
34 changes: 34 additions & 0 deletions test/datetime.t.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1070,6 +1070,9 @@ int main (int, char**)
t.is (Datetime::length ("V"), 2, "length 'V' --> 2");
t.is (Datetime::length ("h"), 2, "length 'h' --> 2");
t.is (Datetime::length ("H"), 2, "length 'H' --> 2");
t.is (Datetime::length ("i"), 2, "length 'i' --> 2");
t.is (Datetime::length ("I"), 2, "length 'I' --> 2");
t.is (Datetime::length ("p"), 2, "length 'p' --> 2");
t.is (Datetime::length ("n"), 2, "length 'n' --> 2");
t.is (Datetime::length ("N"), 2, "length 'N' --> 2");
t.is (Datetime::length ("s"), 2, "length 's' --> 2");
Expand All @@ -1095,6 +1098,9 @@ int main (int, char**)
t.is (r32.toString ("d"), "28", "2015-10-28T12:55:01 -> d -> 28");
t.is (r32.toString ("H"), "12", "2015-10-28T12:55:01 -> H -> 12");
t.is (r32.toString ("h"), "12", "2015-10-28T12:55:01 -> h -> 12");
t.is (r32.toString ("I"), "12", "2015-10-28T12:55:01 -> I -> 12");
t.is (r32.toString ("i"), "12", "2015-10-28T12:55:01 -> i -> 12");
t.is (r32.toString ("p"), "PM", "2015-10-28T12:55:01 -> p -> PM");
t.is (r32.toString ("N"), "55", "2015-10-28T12:55:01 -> N -> 55");
t.is (r32.toString ("n"), "55", "2015-10-28T12:55:01 -> n -> 55");
t.is (r32.toString ("S"), "00", "2015-10-28T12:55:01 -> S -> 01");
Expand All @@ -1109,6 +1115,16 @@ int main (int, char**)
t.is (r32.toString ("j"), "301", "2015-10-28T12:55:01 -> j -> 301");
t.is (r32.toString ("w"), "3", "2015-10-28T12:55:01 -> w -> 3");

Datetime r32a ("2015-10-28T00:05:00");
t.is (r32a.toString ("I"), "12", "2015-10-28T00:05:00 -> I -> 12");
t.is (r32a.toString ("i"), "12", "2015-10-28T00:05:00 -> i -> 12");
t.is (r32a.toString ("p"), "AM", "2015-10-28T00:05:00 -> p -> AM");

Datetime r32b ("2015-10-28T13:05:00");
t.is (r32b.toString ("I"), "01", "2015-10-28T13:05:00 -> I -> 01");
t.is (r32b.toString ("i"), "1", "2015-10-28T13:05:00 -> i -> 1");
t.is (r32b.toString ("p"), "PM", "2015-10-28T13:05:00 -> p -> PM");

// Test all parse options.
Datetime r33 ("2015 10 28 19 28 01", "Y M D H N S");
t.is(r33.year (), 2015, "Y works");
Expand All @@ -1126,6 +1142,24 @@ int main (int, char**)
t.is(r34.minute (), 2, "n works");
t.is(r34.second (), 1, "s works");

Datetime r34a ("2015 10 28 12 00 AM", "Y M D I N p");
t.is(r34a.hour (), 0, "12 AM parses as hour 0");
t.is(r34a.minute (), 0, "12 AM minute works");

Datetime r34b ("2015 10 28 12 00 PM", "Y M D I N p");
t.is(r34b.hour (), 12, "12 PM parses as hour 12");
t.is(r34b.minute (), 0, "12 PM minute works");

Datetime r34c ("2015 10 28 1 30 PM", "Y M D i N p");
t.is(r34c.hour (), 13, "1 PM parses as hour 13");
t.is(r34c.minute (), 30, "1 PM minute works");

Datetime r34d ("2015 10 28 11 45 pm", "Y M D i N p");
t.is(r34d.hour (), 23, "lowercase pm parses as hour 23");
t.is(r34d.minute (), 45, "lowercase pm minute works");

t.notok (Datetime::valid ("2015_10_28_1_30", "Y_M_D_i_N"), "ambiguous 12-hour time without AM/PM is invalid");

Datetime r35 ("Wednesday October 28 2015", "A B D Y");
t.is(r35.year (), 2015, "Y works");
t.is(r35.month (), 10, "B works");
Expand Down
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