Most appraisal reports are prepared to be valid on the date of the report. Sometimes, though, you need to know what a house was worth at some date in the past. These appraisals frequently get prepared as part of an estate valuation, since property in an estate gets valued as of the date that the estate owner died. Most appraisers can produce a backdated appraisal for this or other reasons. You just have to ask them to do it.
Talk to people whom you know are knowledgeable about real estate to collect recommendations for appraisers. If your appraisal is being done as part of an estate, consider leaning heavily on the advice of your estate attorney if you have one. She probably knows appraisers who do a good job with backdated appraisals.
Confirm the license status of any appraisers you are considering. Most state appraisal boards have an online look-up tool on which you can enter an appraiser's name. If your state's board doesn't have an online tool, you should be able to call and check.
Contact the appraisers who are on your short list and who have clean license histories. Let them know what property you need appraised, why you need it appraised and to what date you need it backdated. Ask the appraiser about his experience with similar appraisals and request that he provide you with references with whom you talk. Also, find out how long it will take him to complete the appraisal and what his fee will be.
Hire the appraiser who has the best mix of experience, turn-around time and cost. Talking to references may also give you some insight into what it's like to work with the appraiser.