src/main/java/com/conveyal/gtfs/loader/TimeField.java
@Override
    public String getColumnExpression(String prefix, boolean csvOutput) {
        String columnName = super.getColumnExpression(prefix, csvOutput);
        return csvOutput
            ? String.format("TO_CHAR((%s || ' second')::interval, 'HH24:MI:SS') as %s", columnName, name)
            : columnName;
    }
@Override
    public String getColumnExpression(String prefix, boolean csvOutput) {
        String columnName = super.getColumnExpression(prefix, csvOutput);
        return csvOutput
            ? String.format("TO_CHAR((%s || ' second')::interval, 'HH24:MI:SS') as %s", columnName, name)
            : columnName;
    }
When outputting to csv, return the PostgreSQL syntax to convert seconds since midnight into the time format
HH:MM:SS for the specified field.