CSV export does not respect timezone for Due Date

[kkrasoo]

Bug Description

When exporting a board to .csv, the Due Date field is shifted to UTC instead of using the MSK (Moscow Standard Time) value shown in the card. This causes discrepancies between what users see in the Deck UI and what is exported.

Steps to Reproduce

1. Create a card in Deck with a due date set to 17 Sept 2025, 12:00 MSK.
2. Export the board to .csv.
3. Open the exported file and check the Due Date column.

Expected Behavior

The exported Due Date should match the value in the card (2025-09-17 12:00 MSK).

Actual Behavior

The exported Due Date is shifted to UTC and appears as:

2025-09-17T09:00:00+00:00

This does not correspond to the time displayed in the card.

System Information

• Nextcloud Deck: 1.14.5
• Nextcloud: 30.0.13.1
• Browser/OS: Chrome (tested on Chrome 139.0.0.0). Linux 6.1.0-35-amd64 Scrutinizer Auto-Fixes #1 SMP PREEMPT_DYNAMIC Debian 6.1.137-1 (2025-05-07) x86_64
• Timezone setting: MSK

Root Cause Analysis

The CSV export seems to always use UTC for due dates instead of respecting the user’s timezone configuration in Nextcloud/Deck.

Additional Context

• Manually correcting the exported times is the only workaround.
• This leads to incorrect reports and confuses teams working in a specific timezone.