Yes, you can send your cryptocurrency donation anytime. If you wish to donate to a specific PDAX donation drive, there is a timeframe provided to ensure that your donation will reach the people who need it in a timely manner.
Right now, PDAX accepts cryptocurrency donations for Project Crypto Aid: Covid-19 starting April 1, 2020 until April 30, 2020.
Please note that the wallet addresses used for this initiative are ongoing and will be used for all current and succeeding PDAX donation drives. If your donation is received beyond the said date, it will remain in the respective dedicated wallets of PDAX. They will be held in storage, to be used for future donation drives.