Date of Death
Estate tax liability. Disposition of assets under a will or in probate. There are many situations -- none of them lacking stress and complexity -- where you might need an appraisal of property that states an opinion of what the property was worth on a date some time ago, rather than when the appraisal is ordered. For estate tax purposes or disposition of the assets of a decedent, a "date of death" valuation is often required. (Sometimes, the executor of the estate may choose to have the date be six months after the date of death -- but the same principles apply.)
Attorneys, accountants, executors and others rely on professional appraisers for "date of death" valuations because such appraisals require special expertise and training. They require an appraiser that's been in the area for some time and can effectively research comparable contemporaneous sales.
Real property isn't like publicly traded stock or other items which don't fluctuate in value very much or for which historical public data is available. You need a professional real estate appraiser, bound by the Uniform Standards of Professional Appraisal Practice (USPAP) for a high degree of confidentiality and professionalism and a quality appraisal report.