Bug: DATETIME_FORMAT_V2 hardcodes +0000 timezone, losing timezone information

[hh1985]

Problem

The DATETIME_FORMAT_V2 constant in constants.py hardcodes +0000 (UTC) as the timezone suffix:

DATETIME_FORMAT_V2 = "%Y-%m-%dT%H:%M:%S.000+0000"

This causes timezone information to be lost when formatting datetime objects with non-UTC timezones.

Impact

When creating/updating tasks with a timezone-aware datetime (e.g., Shanghai timezone +08:00), the formatted string incorrectly shows +0000 instead of the actual timezone offset. This can lead to incorrect date display in the TickTick/Dida365 app.

Example

from datetime import datetime
from zoneinfo import ZoneInfo
from ticktick_sdk.models.base import TickTickModel

shanghai_tz = ZoneInfo('Asia/Shanghai')
dt = datetime(2026, 3, 24, 0, 0, 0, tzinfo=shanghai_tz)

formatted = TickTickModel.format_datetime(dt, "v2")
# Current output: 2026-03-24T00:00:00.000+0000  ❌ Wrong timezone!
# Expected output: 2026-03-24T00:00:00.000+0800  ✅ Correct timezone!

Root Cause

The format string uses a hardcoded +0000 literal instead of the %z format specifier.

Proposed Fix

Change line 232 in ticktick_sdk/constants.py:

# Before
DATETIME_FORMAT_V2 = "%Y-%m-%dT%H:%M:%S.000+0000"

# After
DATETIME_FORMAT_V2 = "%Y-%m-%dT%H:%M:%S.000%z"

The %z specifier will output the correct timezone offset (e.g., +0800, +0000, -0500).

Verification

After applying this fix:

dt = datetime(2026, 3, 24, 0, 0, 0, tzinfo=shanghai_tz)
formatted = TickTickModel.format_datetime(dt, "v2")
# Output: 2026-03-24T00:00:00.000+0800  ✅

The task will now be created with the correct timezone information, and the date will display correctly in the user's timezone.

Environment

• ticktick-sdk version: 0.4.3
• Python version: 3.14
• Platform: macOS
• Host: dida365.com (Chinese version)

Thank you for this excellent SDK!