TimeZone identifier

Yes! Amazon Location Service can help with both of these requests. You can use the Geocode API to search for an Addresss, and the Reverse Geocode API to search for a coordinate. In both cases, you need to pass the Time Zone as an additional feature. Here is an example using the Geocode API and the AWS CLI:

aws geo-places geocode --query-text "1600 Pennsylvania Ave, Washington, DC" --additional-features "TimeZone" --intended-usage "Storage"

Which produces the following output:

{
    "PricingBucket": "Stored",
    "ResultItems": [
        {
            "PlaceId": "AQAAAGIAZ4ZMbDpXQkO3SUUnV4Q7_T3NhuQwwvfgSwZz8ggsWZGh9F2dUMvyPFiQqyb1GSNfL17ZiqrsC-jOePvISOXHIec5V2fRNOQDPhPwwW644FJWLaR3IezyJzVdS_qVKlTaWqJxzZhPwxNaFN8K6j3VQvIo1gu2SMDmsinhgJQlxACT1Q",
            "PlaceType": "PointAddress",
            "Title": "1600 Pennsylvania Ave SE, Washington, DC 20003-3228, United States",
            "Address": {
                "Label": "1600 Pennsylvania Ave SE, Washington, DC 20003-3228, United States",
                "Country": {
                    "Code2": "US",
                    "Code3": "USA",
                    "Name": "United States"
                },
                "Region": {
                    "Code": "DC",
                    "Name": "District of Columbia"
                },
                "SubRegion": {
                    "Name": "District of Columbia"
                },
                "Locality": "Washington",
                "District": "Hill East",
                "PostalCode": "20003-3228",
                "Street": "Pennsylvania Ave SE",
                "StreetComponents": [
                    {
                        "BaseName": "Pennsylvania",
                        "Type": "Ave",
                        "TypePlacement": "AfterBaseName",
                        "TypeSeparator": " ",
                        "Suffix": "SE",
                        "Language": "en"
                    }
                ],
                "AddressNumber": "1600"
            },
            "Position": [
                -76.98198,
                38.87908
            ],
            "MapView": [
                -76.98314,
                38.87818,
                -76.98082,
                38.87998
            ],
            "TimeZone": {
                "Name": "America/New_York",
                "Offset": "-04:00",
                "OffsetSeconds": -14400
            },
            "MatchScores": {
                "Overall": 0.99,
                "Components": {
                    "Address": {
                        "Locality": 1.0,
                        "Intersection": [
                            0.94
                        ],
                        "AddressNumber": 1.0
                    }
                }
            }
        }
    ]
}

As you can see you get the Time Zone along with other information about the address. Note you will need the Intended Use option as you plan to persist in a database. This allows you to store the results of the query.

Now for reverse geocode, it's a similar story. Here's an example using AWS CLI:

aws geo-places reverse-geocode --query-position "[-94.71534726352156,39.297533082278115]" --additional-features "TimeZone" --intended-use "Storage"

Which produces the following output:

{
    "PricingBucket": "Stored",
    "ResultItems": [
        {
            "PlaceId": "AQAAAFIA7mDUGDbXf3SUNdF_Fsu9TsMbJ8mfHH_yz4CTCHCwGc5Xq7xqsaUkCk8LuS4_Urg7Fz20xIOJjmj18CimSuqkaxLDsPixe-8g47yJSMxKtKeI7uxPFeWH9JNRpQd3khgCKxjvBzpyHm-CgEQC-o09NnIh",
            "PlaceType": "InterpolatedAddress",
            "Title": "45 S International Sq, Kansas City, MO 64153-1106, United States",
            "Address": {
                "Label": "45 S International Sq, Kansas City, MO 64153-1106, United States",
                "Country": {
                    "Code2": "US",
                    "Code3": "USA",
                    "Name": "United States"
                },
                "Region": {
                    "Code": "MO",
                    "Name": "Missouri"
                },
                "SubRegion": {
                    "Name": "Platte"
                },
                "Locality": "Kansas City",
                "PostalCode": "64153-1106",
                "Street": "S International Sq",
                "StreetComponents": [
                    {
                        "BaseName": "International",
                        "Type": "Sq",
                        "TypePlacement": "AfterBaseName",
                        "TypeSeparator": " ",
                        "Prefix": "S",
                        "Language": "en"
                    }
                ],
                "AddressNumber": "45"
            },
            "Position": [
                -94.71536,
                39.29757
            ],
            "Distance": 5,
            "MapView": [
                -94.71649,
                39.29757,
                -94.71462,
                39.29792
            ],
            "TimeZone": {
                "Name": "America/Chicago",
                "Offset": "-05:00",
                "OffsetSeconds": -18000
            }
        }
    ]
}