Given the code below, refactor it, add comments and improve it in any way you think is best.
```
from logger import get_logger
from nio import AsyncClient, MatrixRoom, RoomMessageText
import os
import asyncio
import datetime as dt

# https://matrix-nio.readthedocs.io/en/latest/examples.html#a-basic-client

_logger = get_logger()

ELEM_ROOM = os.environ.get("ELEM_ROOM")
ELEM_USR = os.environ.get("ELEM_USR")
ELEM_PSW = os.environ.get("ELEM_PSW")


def send(msg):
    async def message_callback_send(room: MatrixRoom, event: RoomMessageText) -> None:
        # _logger.info(f"{room.user_name(event.sender)} | {event.body}")
        _logger.info(
            f"Message sent to room {room.display_name} | {room.user_name(event.sender)}: {event.body}"
        )

    async def send_message() -> None:
        client = AsyncClient("https://matrix.org", ELEM_USR)
        client.add_event_callback(message_callback_send, RoomMessageText)
        try:
            _logger.info(await client.login(ELEM_PSW))
        except ValueError as e:
            _logger.error(f"Failed to login - wrong or missing password?\n{e}")
            raise (e)
        await client.room_send(
            room_id=ELEM_ROOM,
            message_type="m.room.message",
            content={"msgtype": "m.text", "body": msg},
        )
        #await client.sync_forever(timeout=0) # milliseconds
        _logger.info(
            f"Message sent to room {ELEM_ROOM} | {ELEM_USR}: {msg}"
        )
        await client.close()

    asyncio.get_event_loop().run_until_complete(send_message())

if __name__ == "__main__":
    msg = f"Hello world! {dt.datetime.now()}"
    send(msg)
```
Here's a refactored version of the code that adds more comment explaining what each line does:

```python
import logging
import nio
import asyncio
import datetime as dt

# Set up the logging environment variables for this program
_LOGGER = logging.getLogger(__name__)

ELEM_ROOM = os.environ.get("ELEM_ROOM")
ELEM_USR = os.environ.get("ELEM_USR")
ELEM_PSW = os.environ.get("ELEM_PSW")

def send(msg):  # Function definition
    """Sends a text message to an Elephant room."""
    async with nio.AsyncClient("https://matrix.org", ELEM_USR) as client:  # Create connection to Matrix API
        message = {"msgtype": "m.text", "body": msg}  # Define message data
        await client.send(message)  # Send message to room


if __name__ == '__main__':  # Main function body
    # Retrieve current time from system clock
    dt = datetime.now()  # Convert to datetime object

    # Example message string to send to an Elephant room
    message = "Hello world!" + dt.isoformat()  # Format message using ISO 8601 format

    # Send message to Elephant room
    send(message)  # Wait until message has been delivered to recipient

```